Tied because they don't wear my glove or make any noise (arrow ticking), and are easily replaced in the field.
The how to section has a good tutorial. I just tie alternating overhand knots on each side of the string. Take a piece of serving 8" or so, tie it around the string in an overhand knot, paying attention to which side goes over which (like right over left). on the opposite side of the string do the same. Now come back to the original and swap left over right so you have made a square not. Do the same thing on both sides, alternating right over left etc. till you get the size you want. Cut the ends, burn em, drop of super glue...voila. With practice, this knot will stay put but will twist up/down the string if you want it to.