Fishing Knots. This is the one skill that just may save your life one day. Don't put it off. Learn them and do them every day(while you can) for several months, so it's in your muscle memory and you don't forget them. You can't trust that someone else is going to help you or save you ; when you need them to.
The Non Slip Loop Knot. Superb. The strongest loop knot you can tie. Used by big game anglers worldwide. Easy to tie, far stronger and more reliable than the old fashioned strangulating figure eight knot that can substantially weaken line. Ultimate Knots