The 2 biggest keys for river fishing are current and location, with current being the biggest factor. If you have current, go to the nearest current break and fish. Anywhere there's a place for bass to get out the current is good, be it rocks, timber, docks, grass, bulkheads, whatever. It can become overwhelming if you have a lot of targets that can be current breaks. The best advice I can give you there is to fish the type of cover you have confidence in and to look at the surrounding area. If you like to flip shoreline brush or flip docks, then try those places first before you move to others. If your surrounding area has a steep drop, a creek, or a channel swing close by, that would be where I'd fish first. You don't have to fish a current break that's near any of those places just to catch fish, but your numbers and size will usually be in those areas. There are times when you can pick off a fish or two here and there if the cover is significant. You must remember to be accurate with your casts too. That's really important because largemouth in particular, don't like a lot of current. So they'll get up really tight to those current breaks.
If the river you're fishing has little to no current, then the majority of the fish in there are gonna be around cover that's close to a drop, a creek channel, a channel swing, some sort of structure that offers deep water access, cover, and bait. Typically, I catch most of my fish around pads, rocks, and wood that are near to some sort of deep water. You can catch fish in cover that isn't near any of those places, but they're few and far between. I don't fish docks too often but docks that are deep or are next to deep water are best.
It's super important to notice the subtle differences in structure and cover in rivers, as those places typically hold the best fish. What I mean by this is, if you idle over a single stump or tree that's near deep water or in deep water and don't fish it, you're missing out. Most anglers tend to head straight towards the biggest, baddest cover, skipping over those subtle differences. This all holds especially true if the river is a small body of water. Those fish get conditioned to anglers beating up those typical places, and they move off to the more subtle places. Believe it or not, I've hardly ever found large schools of bass. Most of the time there are maybe 3-4 fish in certain areas. You have to cover a lot of water!
Of course, at any given time you can catch a 10 pounder in the most obvious, shallowest place on the river, but I'd say the majority of the quality fish are gonna live deeper, on some sort of structure, near some good cover.
It's also very important to match the hatch on river systems. Typically, the majority of forage species on rivers are smaller, but they're plentiful. Rivers are very fertile and baitfish/prey species often exist in large numbers. I fish the Guadalupe River lakes a lot and I can prove to you that there are some HUGE (6"-10") gizzard shad in there. However, I have my best luck imitating the smaller (3"-5") baitfish/prey species. If you fish a giant swimbait long enough, you'll catch a 10 pounder. But you can also catch a 10 pounder on a 3" bait. You just have to fish the conditions!
If it's early Spring, cloudy, and pre-frontal conditions, I'll normally upsize my baits a good bit because I have an excellent chance at catching a big fish.
Spring: I throw normal size to larger size baits because the fish are active and not too picky. Bluegill baits are a HUGE key to river fishing, and they'll often get you a quality bite. Go as shallow as you can go. Imitating crawfish can be deadly as well!
Summer: This is the toughest time to fish rivers. 90% of the time I downsize or finesse fish. However, early and late I'll use standard size baits. If I'm gonna throw a larger bait, It's gonna be a deep diving crankbait, swimbait, or a plastic. I downsize my jigs, spinnerbaits, crankbaits, etc.
Fall: It's all about the baitfish! Spinnerbaits, paddle tail swimbaits, traps, chatterbaits, anything that resembles a shad. Cover water and go shallow!
Winter: I typically fish pretty slow but hit a lot of different spots. Deep water next to spawning areas are key around January. I stick with a small paddletail swimbait, jig, jigging spoon, and a beaver style plastic. Make sure your bait colors are dull and not lively. Colors like green pumpkin, black/blue, brown, and black are good choices.
I've spent a lot of time fishing river systems and they are hard to figure out. Most of them have their own ways of seasonal changes and they fish differently than lakes or reservoirs. It's all about covering water and spending as much time on the water as you can.
Hope this helps and good luck!
"If people concentrated on the really important things in life, there'd be a shortage of fishing poles." - Doug Larson
"That was like watching the birth of Jesus!"-Urban Fisher