BW,
Jigs are deadly. I think your question is pretty broad after all, different jigs and fishing tactics can be had for all kinds of different fishes, water depths etc. You will need to tailor your jigs to the size fish you wish to target and the depth they hang out at. For sunfish or crappies, I'd recommend jigs at or less than 1/16th ounce. If you are after bass you will likely need to go heavier. My personal preference is for jigs made of natural material rather than soft plastics. I tie my own jigs using marabou and/or deer hair. I think natural materials are superior in virtually every way (including cost if you're a fly tier) than plastic. I also like to tie a mono loop weed guard on many of my jigs if you intend to fish a lot of rocks or cover. If you are fishing from a boat with electronics that can "read" fish and indicate their depth, your best bet (esp if they are deeper than about 15') is to drop the jig straight down and vertical jig. Try experimenting with different sizes/styles and see what works. If all else fails, try tipping your jigs with a live minnow, chub, or piece of worm.
Good luck.