I am absolutly no expert, and have very limited experience with swimbaits but I'll take a stab anyway.
The charlies are pretty bad. Save your maney and get a few higher priced better quality SB's. I have around 15 charlies and most of them ran crooked out of the package.
Pick your color according to the water color. If the water is clear, throw a SB that is as natural as possible. If it is muddy, throw something dark. If the water is moderatly stained I like a chartruese, or other bright color.
The bigger the lure, the bigger the fish......usually. Sometimes you'll get a greedy little dink whos eyes are bigger than he is.
Make sure your using the proper gear. You'll need a rod that can throw a lure that weighs 1=4 ounces. You'll need line ranging from 17#-25# and maybe more.
Check out this article by fourbiz from the forum. He is a cali-trained swimbaiter.
http://www.bassresource.com/fishing/swimbait_gear.html