You will use anchors more frequently when cruising in a dinghy than when racing or just pottering around. If you sleep on board your dinghy you may often find it simpler to anchor overnight rather than getting permission to use a mooring or finding a berth alongside. You may also want to anchor to go ashore for sightseeing or shopping and you will want your boat to stay where you left it rather than drift away and possibly cause damage to expensive yachts. However there is no need to get paranoid about this, if you have good anchors and warps and anchor on suitable holding ground you should have no problems.
The Dinghy Cruising Association offers a useful guideline that a traditional fisherman style anchor for a cruising dinghy should weigh about one pound for each foot length of dinghy. It is also stated that if you use one of the more modern anchor styles with broad flukes the anchor weight can be reduced to two thirds of that recommended for a fisherman anchor. It is generally accepted that broad fluked anchors such as the CQR, the Bruce and the Danforth hold better than a fisherman on a soft seabed, eg soft mud, and this is hardly surprising. On the other hand, a fisherman anchor is at least as good, and indeed probably better than, the modern anchors when the seabed is stones or is overlaid with kelp. I certainly would not write off the fisherman anchor as an obsolete design, it is a reliable anchor under a wide variety of conditions, even if it does not quite have the best holding ability on soft seabeds, which are in any case not the kind of seabed which usually causes trouble with anchoring.
I have seen published test results for the holding ability of different anchors but the results seem rather inconclusive. Holding ability probably depends more on the type of sea bed than the type of anchor and this makes comparison difficult. Certain sea beds such as shingle provide very poor holding for any type of anchor and if you need to anchor securely you simply have to avoid anchoring on this type of seabed altogether. We have used various anchors with the HSC club boats and I think that only the Danforth type has let us down, having on one occasion allowed both our boats to go adrift. The local sailing school retrieved them for us. I cannot be sure that this was the fault of the anchor itself but it does look to me as though the Danforth anchor could be prone to getting jammed up with debris from the sea bed. Suppose that the anchor drags a bit before it bites home then something like an old boot or a clump of sea weed lying on the seabed gets stuck between the shank and the flukes. Then if the tide turns and the anchor topples over the other way up the flukes will be locked pointing upwards and unable to dig in. This is only a theory but it makes me a bit wary of Danforth anchors even although they are a convenient flat shape to stow and have large flukes for maximum grip in soft mud. I have a CQR anchor and have found this to be reliable to date. The Bruce anchor is another type which has good reports from users. Both the Bruce and the CQR anchors are rather awkward shapes to stow. The traditional fisherman anchor folds up and is then a good shape for stowage but it does take a few seconds to unfold it if you need it in a big hurry. Incidentally Roger Barnes of the DCA has provided a tip to speed up the deployment of a fisherman anchor. This is to lock the stock in place not with a metal wedge and lashing as usually provided with the anchor but with a hairpin shaped stainless steel spring clip which you can buy from a good chandlers.
It is often suggested that a dinghy should be anchored with a short length of chain attached between the anchor and a warp (rope). The idea is that the weight of the chain improves the direction of pull on the anchor and improves holding. I would question whether it would not be at least as good simply to use a correspondingly heavier anchor without the chain. I have tried using chain on a dinghy anchor and have found it awkward to handle. It can do a lot of damage to varnish work or pristine fibreglass and it will not run properly through the small fairleads or other bow fittings on most dinghy sized boats. I prefer just to have a plain rope and with the DCA recommended anchor weight and adequate length of rope (scope) this seems fine. I don't think I have ever dragged the anchor on my own boat other than when anchoring on unsuitable ground (famous last words!).
Incidentally, the idea that chain lying on the seabed provides a valuable shock absorbing effect is questionable, analysis shows that this only works in moderate conditions and that under conditions when the ground tackle is heavily loaded the shock absorbing capacity due to a chain catenary is actually less than that provided by a nylon rode - various studies confirm this eg. https://www.petersmith.net.nz/boat-anchors/catenary.php
The recommended material for an anchor rope is nylon since it is has high strength for a given diameter and is slightly stretchy so it can absorb shock loads. Anchor ropes for dinghies tend to be oversized in terms of ultimate strength and so for practical purposes polyester is probably almost as good as nylon and is available in a wider range of colours and plaiting styles. The floating ropes such as polypropylene are to be avoided for this purpose since an anchor rope floating on the surface could catch motor boat propellers. Plaited rope seems to tangle a bit less than the traditional laid (3 strand) rope and is usually more comfortable to handle. I used to use 10mm diameter rope to anchor our boat but have now changed to 8mm 'Anchorplait' nylon (available from Liros ropes and possibly other manufacturers) since we don't have a lot of space for stowing the rope. I would not go any smaller than 8mm since although a smaller rope may be quite strong enough in new condition it will not allow much margin to allow for wear by chafing.
I find the easiest way to keep a long rope such as an anchor rope free of tangles is to dump it into an open topped container as the anchor is hauled in then just let it run out from the container when the anchor is next lowered. A suitable container is a plastic bucket, washing up bowl or small basket. A small hole at the bottom of the container will provide drainage and another hole will allow the free end of the rope to be lead out so that it can tied to some part of the boat. No attempt should be made to coil the rope in the container, the more untidy it looks the better it will run out when needed. Contrary to what most people would think, coiling ropes neatly is a sure way to get them in really bad tangles! 100 feet length of rope on each of two anchors is sufficient for cruising in most areas. It is usually stated that the length of anchor rope should be five times the water depth. Hence in most areas 100 foot length will allow you to anchor at high tide and be sure of not grounding at low tide, as may be necessary if you are not sure that the bottom is safe for the boat to ground on. If you sail in areas such as the west coast of Scotland where the water is often deep even close to the shore it would do no harm to have even longer anchor ropes.
At this point I would mention a strange and rather annoying property of certain modern synthetic ropes. I purchased a 10mm diameter plaited nylon anchor warp and found that after a couple of years use it had increased in diameter to something like 15mm. I asked about this at a chandlers shop and was told that it is due to the fibres bunching up with use. I am sure that the extra diameter does not increase the strength of the rope one iota since there are still the same number of fibres in the cross section but it may reduce the length and it certainly increases the storage space required for the rope. I have another plaited nylon warp which has not grown in diameter at all with use, I wonder what is the difference.
I think there is much to be said for having two anchors and warps when dinghy cruising. One of the main reasons is that the use of two anchors allows you to restrict the space your boat can swing through when at anchor. This can be essential if you need to anchor in proximity to other boats or obstructions. Two anchors also allows more secure anchoring since the two anchors can be placed so that they are always loaded in roughly the same direction and hence less likely to pull out as the tide turns. It is sometimes useful to anchor with one of two anchors on the beach so that you can pull your anchored boat to the shore. Finally, two anchors provides a backup if you loose one of them. The most likely reason for loosing an anchor (apart from not tying it to the boat) is getting it inextricably tangled in some debris on the sea bed. This is fairly unlikely but it can happen. It has happened to me twice but so far only in water shallow enough that I have been able to get the anchor back by going swimming. Of course, if you are rash enough to anchor in proximity to laid moorings you considerably increase the risk of loosing your anchor.
Two anchors laid at 120 degrees. - Swinging space shaded grey compared with swinging space for one anchor as dotted red circle
When anchoring with two anchors a typical technique is as follows. You drop the first anchor while still sailing, rowing or motoring. Then with the boat still moving you run out the warp until you reach the position where you want the second anchor. Often this will require the full length of the rope or perhaps the rope from the second anchor temporarily joined onto that from the first. As soon as the second anchor is down you lower sail or stop rowing or motoring and then adjust the two warps. Probably you will aim to have about the same length of warp on each anchor and an angle of around 120 degrees between the two warps. This angle gives roughly the same holding strength whichever way the wind blows your boat. Furthermore, as noted above, with a fairly large angle between the ropes the pull on each anchor is always in roughly the same direction even when the wind and/or tide turns. Anchored in this fashion your boat should be secure and it will also take up a lot less swinging space than with a single anchor, even if a chain cable were to be used with that single anchor. You may want to anchor for an extended period, perhaps to park the boat between two weekends. In this case if you have ropes to two anchors secured within the boat the two ropes will probably get twisted together as the tide repeatedly turns. I have never yet found this to be a problem, you don't usually get that many twists since if there is any wind a half twist made by the flood is more than likely going to be untwisted by the ebb. If you want to avoid twists in the ropes you can join one rope to the other using a rolling hitch outside the boat but then you loose the slight extra security of having both anchors individually fastened to the boat.
Quite frequently one wants to anchor the boat and go ashore awhile leaving the boat so that it will not ground when the tide ebbs or so that you can still return to it when the tide floods. If the wind is offshore and there is not much current this is usually just a matter of placing an anchor on the beach letting out plenty of rope then giving the boat a push off - see diagram below. The anchor rope must be long enough to keep the boat clear of any small waves breaking on the beach since these will tend to drive the boat back to the beach despite the offshore wind. The length of anchor rope and position of the anchor on the beach must also take account of the rise/fall of tide expected during the period the boat is to be anchored.
Anchoring with offshore wind and single anchor placed on beach - This only works if there is little or no current.
If the wind is not truly offshore or if there is any significant current a single anchor will probably fail to hold the boat clear of the beach. The boat will end up lying on the beach and if there are even small waves breaking on the beach this is not good for the boat. Also, on shingle beaches there is a good chance of getting the centreboard jammed up with small stones. A more certain way to hold the boat clear of the beach is to use two anchors, one to anchor the boat suitably clear of the shore and one on the beach to pull the boat back in when you whish to re-board - see sketch below.
Anchoring with one anchor on beach and one offshore - This works with some current and even with the wind in a direction slightly onshore.
If the tide is ebbing the time you can spend ashore before your boat grounds will be limited by the length of rope - another reason for not stinting on the length of anchor rope. If the tide is flooding you also need a long rope to get the anchor far enough up the beach that you can reach it later without swimming.
If the wind is onshore, i.e. it is a lee shore, or if there is almost no wind at all it is possible to anchor using a pulley attached to the anchor. A long rope is lead from the boat, through the pulley, then to a second anchor on the shore then back to the boat. The boat can then be pulled in and out as required. This arrangement is quite complicated to set up and in most situations it is easier just to find a windward shore to anchor on. The length of rope required probably means you will need to join both your anchor ropes together and the knot must be the right side of the pulley. There can be difficulties if seaweed gets jammed in the pulley. The load on the anchor is doubled compared with normal anchoring so you need to be sure of good holding ground. A large free running pulley works best and I keep one on board for this purpose but don't use it very often. I have also heard of a large metal ring attached to the anchor being used rather than a pulley, perhaps this might be a little less prone to jamming up with seaweed.
Anchoring with a line through a pulley attached to an anchor - Keeps the boat afloat in an onshore wind but can be tricky to set up properly.
The above notes on anchoring on the shoreline are really only applicable when there are no significant waves, that is in calm weather or where there is shelter as in a good harbour. If there are waves of any size breaking on the shore then landing will at best result in a soaking and getting away from the shore again will be even harder than landing. Lee shores with breaking waves are particularly unfriendly places for any kind of boat and whilst a dinghy may well survive better than a larger boat it is not wise to take chances with lee shores.