Be aware that you can pull up snappers, gar, and a huge variety of fish, but if you are in catfish rich waters, using the bait catfish like best, you are going to get yourself some catfish. Just try to cause as little motion on the water as you can, because as soon as you get your catch off the hook, you are going to want to rebait, and put your jug back out on the water.
To make your jugging experience the best it can be, here are some tips:
Consider either purchasing specially designed jugs from bait houses or sporting goods stores that have reflective surfaces to help you see your jugs in the dark (most jugging takes place at night) or paint the half of your jug that will be out of the water a bright color like yellow or orange. This will help you to be able to see, not only where your jugs are, but exactly when you get a bite.
If there is a strong current in the water where you are fishing, put some sand or gravel into the jugs to help weigh them down and hold them in place. Another benefit to putting the sand into the jug is that when you get a bite, it will pull the sand into one corner of the jug, and cause it to stand up in the water. That makes it very easy to tell when you get a bite.