Surely one of the greatest joys of the canal network is that, by and large, you can moor anywhere along its 2,000 or so miles. As you chug along, you can just spot a nice location and think “here will do!” and stop. At least, that’s the case with canals. Rivers are a different matter, as explained here.
That said, there are a few restrictions. You mustn’t moor on the non-towpath side unless it’s specifically marked to do so; usually the offside is privately owned and without the landowner’s consent, it would be trespass to tie up there. More practically, the offside is also often very shallow and silted up so it can be difficult to pull in properly anyway.
You also mustn’t moor so as to cause an obstruction or nuisance which means no mooring on the water points (other than just for as long as you need to refill your tank), or in bridge holes or in winding holes or on lock landings or where signed as no mooring.
I’d say it’s common sense except that for a handful of boaters, such sense often seems to have deserted them.
The art to mooring is to point your boat towards the side and chug very gently towards it. Just as you’re about to thump the bank, turn the tiller or wheel so as to steer the boat parallel to the side, and use as little throttle as possible (I often alternate between going into neutral and just a burst of tickover) so as to bring the back of the boat in as well. If you have anyone else aboard, they can jump off when it’s suitable to do so, clutching the centreline, and then pull the boat in to the bank. If you’re single-handed, you need to jump off in which case definitely don’t forget the centreline and don’t forget to drop the engine into neutral else it’ll be you vs engine.
Once the boat is stopped and lying alongside the bank, you can tie the boat at the bow and stern. Canals having mostly no flow, it’s even feasible for a solo boater to just let go of the centreline and scurry ‘twixt bow and stern while tying up though beware that any passing boats will cause a suction effect that pulls the boat first back, then forwards, quite powerfully so you’ll need to keep an eye out and be ready to grab that centreline again so that the boat doesn’t drift off into the middle of the canal with you staring on helplessly from shore.
The most secure way to moor is against metal railings (generally referred to as “Armco” though I believe this is actually a trade name) which are piled into the bank. You can thread a mooring chain through the back of the Armco and then tie that to your mooring ropes. Once you’ve done one end of the boat, pull the rope at the other end so as to hold the boat tight, and secure that. Remember to put your fenders out on that side first so that the metal (and any bolts sticking out from it, which is not uncommon) don’t scratch your paintwork.
An alternative to chains is ‘nappy pins’ (Americans would call them diaper pins) which hook behind the Armco but I always find them to hang a bit loose so they can rattle and squeak as the boat moves about which is tiresome.
In the event there’s no metalwork to tie to, you’ll need to moor the old-fashioned way which is like staking out a tent. You hammer metal spikes (mooring pins) into the ground as far as they’ll go and tie your ropes through the end. It’s best to angle the pins away from the boat so that any movement has less chance of pulling the pin from the ground. Beware, this does happen, particularly if passing boats come by too fast – as mentioned, their movement will ‘suck’ your boat forwards and backwards which can loosen mooring pins. It’s not uncommon to find boats adrift because of this, though since there’s little flow on the canals, such unfortunate boats tend to do little more than end up halfway across the canal.