Making a Fireman's Coil
It's a basic fact of all boats. Any length of rope longer than 3 feet will magically knot and tangle itself. To avoid this there are a number of coiling knots that have been devised.
This one is called the Fireman's Coil. I don't know if it's the best but it's the one I can remember so I use it. It's usually the first one you learn when you start sailing.
I use this in particular when I coil up the end of my halyards and just hook it on the cleat that lives on the mast after I've raised the main sail and the jib. When I plan to put the rope in a locker I usually do a second loop through the first and tighten extra well.
Fireman's Coil with extra Loop
If the rope is going into a locker and not being hung up I tie the bottom too. I have small bits of rope and just make a quick reef knot at the bottom of the coil. I don't complete the reef knot but rather leave a loop so I can just pull one end and it unties. It's not a critical knot so the reef knot is ok there. Don't use it where your safety is at stake, it's not reliable.
When I tidy up the boat after I've come in from a sail, I put a fireman's coil with a double loop in my main sheet and hang it up from the end of th boom. It keep it out of trouble and untangled.
This web site reflects my personal ideas and doesn't represent anyone else's point of view.