Most people peg them about 2" above the hook with a toothpick but I do it a little differently thanks to some insight from a friend... I place the bead on the line, tie on my hook and then I tie a nail knot with 20lb mono onto the leader below the bead and about 2" above the hook. I cut the tag end off closest to the hook but leave the tag end about 1/4" long on the upper end of the knot. The tag end keeps the bead from sliding over the nail knot. It works really good. Every fish I caught this year has been in the mouth also. I have also found that if you slide the nail knot into the bead as well, the bead pretty much stays pegged.
This variation is a little more durable as a toothpick can get water logged and fail on you.
I'll see if I can use my MS Paint skills to draw a picture and post it later.
Edit: Here's my lame attempt at a diagram