Your standard earthworm or nightcrawler is a popular live bait for many fish, and bluegill are no exception. Worms give off a pungent aroma in the water that appeals to bluegill. You don't want to use too large nightcrawlers, because bluegill tend to be smaller fish and might not be interested in a large bait, but it's worth trying if you're trying to land a trophy fish. Otherwise, your standard earthworm will attract attention from bluegill of all sizes. Crickets and grasshoppers are also popular options.
Sometimes, the larger bluegill can be more selective. Larvae, however, is often a sure bet with all bluegill, particularly larvae of bee moths, spikes or mousies. You can stick these larvae on an Aberdeen hook and drop them in the water. They'll probably sink even without a spit shot or sinker.
During spawning season in early summer, many bluegill are hesitant to leave their spawning beds for fear of losing their spawn to predators. When this happens, artificial baits need to be used to draw the fish away from their beds. The flashy colors on artificial baits usually do the trick. There are a lot of baits you can try that are likely to succeed, including in-line spinners, small plastic worms, floating stick baits, mini crankbaits and tiny jigs. Remember that bluegill mouths are small, and smaller baits will open you up to a wider range of fish.
When the fish are hungry--wintertime is a good bet--almost anything works on bluegill, including hot dogs. Stick to cheap baits if you know the food supply in the water is scarce. It'll save you money, and it won't reduce your effectiveness when fishing.