The idea with the dropper nymph is to give the fish options...the wet fly usually just gets their attention, and rides higher in the water column. Also, it lets you cover more ground as you troll/retrieve. Then fish at different depths will get a good look. Keep in mind, this method only works when the fish have been located close to the surface (i.e. you see rises or get bites near the surface).

A Woolley Worm will work fine for the wet fly. As far as attaching the dropper, the easiest way I have found is to tie a 12''-18" section of tippet to the shank of the wet fly and then tie the nymph to this leader. If you want to do it like the Brits, tie a third leader section to the nymph and attach another fly so you end up with a three-fly rig (check your regs for the lake though, some lakes are not cool with this).

This "dropper" method is how most of the smug river fisherman get so lucky on a regular basis, don't believe any fairtales you hear about them nailing em all on dries. I guess the sun shines on everyone once in a while, but in my experience the guys catching lots of fish are hedging their bets with lightning bugs and copper john's...