The best tip I can think of that will cover most situations, is to maintain a mental edge. Sometimes after hours of casting, drifting, etc... with no results, it's easy to just kind of go through the motions. If you try to remain focused, no matter how bad the fishing seems at the moment, I think the end result will always be better. This doesn't mean be obsessive, and forget about everything and everyone around you, just try to be a little more in tune with the feel of the drift, or the look of the water etc...

Awareness of what other fisherman around you are having success with, and being sure that you have whatever technique you are using dialed, should equal more hookups, and more fish landed.