I use a little differnt type of lanyard then the ones you see in the orvice shops. I saw some pretty inexpensive ones at Ikea (you never know where you will find useful fly fishing gear) and I brought home a dozen of them. Here is how I use them:

The lanyards have detachable ends. Each detachable end has both a dacron loop and mini key-type ring, and a hook with a spring loaded keeper (like a miniature dog leash end). The ends are fastened to variuos accessories like fly boxes, nippers etc.. I place one lanyard around my neck and snap on whichever tool or accessory I need at one time. The other lanyards are left at home or in my gear bag in the car. So I end up with one lanyard around my neck that can accept different attachments. The ends which are fastened to the acessories that are not being used can be hooked on to "D" rings on your vest (I use a Fishpond ChestPack)so they don't fall in the water and drift away when they are not being used or stowed in pockets. I have had to chase a flybox downstream on occasion and I like the idea of clipping them to something while I am selecting flies incase I fumble and drop one.

Another important feature is the safety device (weak link) that breaks away if it gets snagged so you don't strangle yourself or get pulled in the water by a passing drift boat