The Bowline is the most respected knot for creating a loop in the end of a line that will not slip. There are many ways to tie this knot and, although complex, the knot can be easily learned. The Boy Scout method uses a story of a rabbit (working part), a tree (the standing part) and a hole (a loop) at the base of the tree. Once the hole is formed, the rabbit comes out of the hole, goes around the tree, and then goes back down into the hole.
Place an overhand loop about the size of the palm of your hand in the working part of the line approximately three times as far from the bitter end as the length of the loop you want to tie. Hold this loop with your thumb and fingers of your non-dominant hand to maintain the loop. With your dominant hand, pass the working part up through the loop as in A.
Pass the working part of the line behind the standing part of the line and back down through the loop as in B. You should have about 3 inches of the bitter end of the line now inside the large loop that the bowline is forming.
To finish the knot, seize together with your dominant hand the bitter end and the part of the large loop next to it and move your non-dominant hand from holding the small loop to holding the standing part of the line.
Pull the standing part of the line away from the knot to tighten while holding the bitter end and the loop fast, as in C.
A variation of the bowline used by many boaters to create a loop that will not seize when wrapped around a pylon takes the bitter end around the standing part in the other direction before running it back down through the small loop. This places the bitter end on the outside of the large loop where it will not seize against the pylon. Either way works.