You need to get some treble/dough hooks, because the best baits are going to fall of regular hooks. Chicken liver (a little old and stinky, but doesn't have to be rotten), and stink bait (you can make your own and it's usually better than the storebought, look online for recipes - though, Sonny's is a good brand for premade http://www.zeiners.com/sonnysstinkdipbait.html - we caught a whole bunch of flatheads and channels on this last time). I also use homemade dough balls made from bread mixed with all kinds of random smelly stuff including fish flake or pellet. Remember, SMELL, that's how they hunt, make sure to make it smelly with stuff you think they'd like.
You can also try all kinds of meats, and it doesn't have to be fresh. Any fish filet you can find at the store, or whole pieces of fish, crayfish tails or whole crayfish (flatheads love crayfish), fake crab, chicken, beef liver or beef (many people swear by beef that has been sitting in the sun), etc..
You need to be fishing on the bottom with enough weight that your bait is staying in one general place. I use a simple carolina rig, which is especially good for rivers/moving water, but can be used anywhere(http://catfishtraining.com/carolina-rig - and the way you rig DOES matter) And then LEAVE it. Don't keep pulling it in and casting, though you can pull in if you have a bite, or after about 10 mins to make sure bait is still there. You want to leave it as long as possible because they hunt by smell, and you need to give them time to get to it. Catfish will usually be in schools and if you start getting bites you will catch several for a while until that school moves on, then you'll be left waiting for another school to come along.
Someone mentioned minnows. Minnows are fine, and sometimes that's what they're mostly biting on. We use whole sunfish for trot lines. Just make sure you're weighted enough to keep the minnow from swimming around everywhere (one, the catfish will have a harder time grabbing it or finding it, and two the minnow will tangle your line around something). Catfish bite good on sunfish, chubs, goldfish (legal to use here since they're already introduced but not everywhere), and especially shad (shad have a strong smell - you can even use whole dead prepackaged shad from the bait section). The minnows don't even have to be alive and may attract them better when dead and stinky. Use minnows that are at least 4 inches long. If you use tiny ones they're going to get nibbled off quickly by sunfish. Even small catfish will take fairly large minnows. Hook the minnows through the back, not through the mouth so they don't just get taken off.
The above is the most important things. There are other things you can do, but if you follow the above rules you should be catching them if they're around. And as others mentioned they will be biting most early morning and late at night. At night they are probably starting around 8-9pm this time of year. Since you are mostly relegated to daytime, fish near the shoreline where there are holes, and around root wads, driftwood, rocks etc. since that's where most catfish are going to be hanging out during daylight. Some people think they need to cast out real far and get into deep water, but actually you stand a great chance catching catfish not far out from shore or even right next to shore. I've seen big ones sitting right at the shore resting MANY times.
You can also try all kinds of meats, and it doesn't have to be fresh. Any fish filet you can find at the store, or whole pieces of fish, crayfish tails or whole crayfish (flatheads love crayfish), fake crab, chicken, beef liver or beef (many people swear by beef that has been sitting in the sun), etc..
You need to be fishing on the bottom with enough weight that your bait is staying in one general place. I use a simple carolina rig, which is especially good for rivers/moving water, but can be used anywhere(http://catfishtraining.com/carolina-rig - and the way you rig DOES matter) And then LEAVE it. Don't keep pulling it in and casting, though you can pull in if you have a bite, or after about 10 mins to make sure bait is still there. You want to leave it as long as possible because they hunt by smell, and you need to give them time to get to it. Catfish will usually be in schools and if you start getting bites you will catch several for a while until that school moves on, then you'll be left waiting for another school to come along.
Someone mentioned minnows. Minnows are fine, and sometimes that's what they're mostly biting on. We use whole sunfish for trot lines. Just make sure you're weighted enough to keep the minnow from swimming around everywhere (one, the catfish will have a harder time grabbing it or finding it, and two the minnow will tangle your line around something). Catfish bite good on sunfish, chubs, goldfish (legal to use here since they're already introduced but not everywhere), and especially shad (shad have a strong smell - you can even use whole dead prepackaged shad from the bait section). The minnows don't even have to be alive and may attract them better when dead and stinky. Use minnows that are at least 4 inches long. If you use tiny ones they're going to get nibbled off quickly by sunfish. Even small catfish will take fairly large minnows. Hook the minnows through the back, not through the mouth so they don't just get taken off.
The above is the most important things. There are other things you can do, but if you follow the above rules you should be catching them if they're around. And as others mentioned they will be biting most early morning and late at night. At night they are probably starting around 8-9pm this time of year. Since you are mostly relegated to daytime, fish near the shoreline where there are holes, and around root wads, driftwood, rocks etc. since that's where most catfish are going to be hanging out during daylight. Some people think they need to cast out real far and get into deep water, but actually you stand a great chance catching catfish not far out from shore or even right next to shore. I've seen big ones sitting right at the shore resting MANY times.