The drop shot (d-shot) is a very versatile way to fish plastics - big and small. Basically you tie s hook on your line with a Palomar knot and leave the desired length of tag line. On the end of the tag line, you attach your weight and when it pulls your line tight, the hook should stand out perpendicular to the line (making it stick straight out),
I believe the origins of the d-shot were when bass fishermen were trying to find a new way to fish finesse baits in holes that were holding bass or tight to structure. You would basically fish directly below your boat and jig, twitch or dead stick your bait.
BUT... you can do ALMOST anything with a drop shot. Using a drop shot, I've caught fish in boils, I've caught fish directly below me, I've caught fish flipping into brush, I caught fish worming the d-shot like a Carolina rig and I've caught fish on a d-shot accidentally.

:roll:
The basic ideal is to use a small drop shot hook, a bait about 4" long and a small weight on the end of a tag line that's about 4 to 12 inches long. However, I use #2 to 1/0 Gamakatsu Wide Gap hooks and I'll use baits from 3" to 7" long. I typically don't use more than 12" of tag line and I like using a brass bullet sinker with one or two glass beads below it (pegged to stop the brass) for a little added clack. Some people talk about using very light line while others will beef it up with 20lb test and fish it in very heavy cover with big baits. It's really a very versatile rig.
I'm not the D-shot God or pro, but I like using it a lot. Just start off with the basic d-shot and take it from there. Find what works best with your style and what you like doing with it. Here's a link for some info and book mark the home page of this site, it's a helpful link.
http://www.bassresource.com/features/worm_rigs.html