Fish in rivers aren't going to behave the same as fish in a lake. About half of my fishing is done on rivers here in the South but the principles should still apply. The main thing to look for outside of visible cover is any kind of current break in the water whether it be an eddy or seamline (an area where shallow faster water meets deeper slower moving water). Fish those areas. Keep in mind that you are going to be on the move constantly, so you may pick up two or three fish in one area but you may not sit in one spot to do it. I kind of look at it like running and gunning. I'll throw to a spot a couple of times then move on, if I pick up a fish I may throw to a few more spot around where I caught that one then I keep moving. Notice what is working for you and repeat but keep moving. I have had times when I've absolutely hammered them at the mouth of a creek but those time are few and far between. Generally most of my time is spent on the move. Also keep in mind that a river is a living thing, the river you fished today isn't the same river you will fish tomorrow.