I'm a total newbie and often have a similar issue at the spots most convenient to me. What helps me (as weird as it might sound) is to keep a few small hooks and Powerbait (crappie nibbles in the chroma glow colors) around. If I'm not even getting so much as a nibble, i toss on the small hook and the powerbait and see what I catch-if nothing really emerges, I know there's zilch in the area and move on. If I get hit 3, 4, 5 times catching sunfish, I know there's fish around and I try a few other lures or move to a new angle.
Now, having said that, I'm fishing highly pressured parts of NJ, so I've caught all of two decent size bass, both of which I lost while reeling them in, but I still like the Powerbait method as a way of figuring out if the fish are even hanging out where I am. Also, it takes the sting out of being skunked if I can at least snag a few sunnies. Plus it entertains my son when we can pull SOMETHING out of the water (besides weeds).