I use both soured milo and range cubes, sometimes both in baiting the same holes. When you catch a few, look to see what they spit up, then continue to chum other holes with that one.
Cubes are a lot cleaner and easier to use, soured milo is cheaper, but the smell of either will attract them.
Stubby's Cheese Bait is also a staple. Like he says, other baits work too, but his is easy and very effective and consistently works for me.