How do you catch bigger catfish?

I fish in a little cove on Boone Lake(I think its a reservoir,so it has a slow current).I usually catch catfish up to 6 or 7 pounds.How do i catch bigger ones?Do i throw out in the middle or use a different bait?(I use cut up bluegill for bait and it works really good,but f you know any better bait I might try them).