It all depends on just what kind of fishing I'm doing, but first and foremost the old KISS (keep it simple stupid) axiom always applies.
When fishing for channel cats, I usually use spinning equiupment and no more than a 12 pound test line. When I'm fishing for spawning channels I fish along a rocky bank and cast to the bank and allow my bait so sink fishing like you would do using a jig for crappie. I never use a leader, just tie the hook to the line, use a small split shot a foot or so above the bait....shrimp, minnows, night crawlers. If you use shrimp get the kind you would buy to cook and peel to eat, They are much nicer than the crappy bait shrimp...keep em cool and clean and cook what you have left over.
Sometimes I float a bait for channels. Spinning equipment works well and a slip cork. I like those bait holder hooks, but I sure can't remember what size....not very big, just big enough to hold a shrimp.
If I fish for blues or flatheads I use casting equipment. The Ambassadeur 6500 C-3's are great, and a 7-8 foot rod. I like those Ugly sticks..one piece rods, but also use a bass 7 ft. flippin stick. I usually drift using shad for bait, or if after flats a live perch. I put around a two ounce sinker on bottom, and tie a dropper loop a couple of feet above the sinker for my hook. I use different sized circle hooks for this type of fishing. About the heaviest line I use is around 17 pound test.
I do all my cat fishing out of a boat.
There are times when I need more weight, and times when I use fairly large hooks, that all depends on wind, current, bait size. Like I said though....it's always a pretty simple set up.