Use high quality hooks. They cost a lot of money but they are the item that does the actually catching of the fish. The sizes and shapes are really varied these days. I like thin wire, wide gap, short shank. Beware of red hooks because since they are popular, many companies make them and the red paint either is rough, the hook is not sharp enough or the red paint comes off.
Treble hooks can be tiny and still work perfectly if they are not gobbed up with a lot of bait. Otherwise, the size of the single hook depends on the size of the bait. I always expose the point of the hook. I don't want the bait to get in the way.
