WEEDS - aquatic vegetation provides great ambush cover for them to feed. I have watched a pickerel charge out of thick weeds in a foot of water to grab my bait.
and for river fishing of all kinds, there are two words to remember:
current breaks
anything that breaks the current, be it a rock, a log, a shoreline point, anything, has the potential to hold fish.
Fish will almost always face into the current, so bring your bait with the current, or quartering, to bring it to them in a natural fashion. A bait coming up behind them will usually spook em.
The edges of current where faster water meets slower water is an often overlooked 'spot on the spot'. Outside corners of turns will be deeper/faster, because the current digs into it as it comes around the turn - inside corners(especially the downstream side) will be slower/shallower... and often better fish holding spots.
They all go riffle > hole > run, riffle > hole > run, etc.... this applies to the smallest stream or the biggest river. 'Riffles' are more turbulent(like rapids) due to the hard bed the water is flowing over... when it gets to softer bed, it digs out a 'hole'... then the hole usually gently smooths out, making the 'run'. This could be 50 yards or several miles - - it's the same, only the scale changes.
(not trying to write a book, I just like stream/river fishing. We used to hammer the smallies in moving water back home in OK)