A bobber is used whenever your bait is not moving in teh water. Normally, you'd have to look at your pole to see if it flexes when a fish bites. With a bobber, you can look towards the water. It's also used for fish that like to nibble at your bait, and don't ''bite it and run off.'' Trout, and other smaller freshwater fishing use this.
Put the bobber wherever you want the bait to stay. For example, if you put the bobber 15 feet from the bait, the bait will sink only 15 feet.
Bass can be caught in the most common three ways of freshwater fishing; Lure, Troll, and Fly.
You're fishing by lure, letting the bait sit. This does work, but better in areas that have lots of cover; Behind a cliff, under trees, near downed logs, or in forests of aquatic plants. Note, that your lure may get tangled. Worms, feathery baits, flesh, etc. are all used.
If you troll, baits that are shiny, spin, resemble a fish or other meat baits all work. Cast out and reel in, or run your boat slowly, with your bait behind. Depending on the speed, and depth of the bait, you can place your bait anywhere from 10-40 feet behind your boat. You'll probably want to add more weight if trolling.
For fly fishing, well.. you have to know how to cast.
All different methods have different results. Improvise, until you find a method you like, or is successful. Ask other anglers or watch their techniques if you want some hints.