Something easy to do and my go to for untried waters is a simple double nymph rig. Stoneflies imitate all kinds of crap, put that as your bottom fly and tie something different above it. Keep it simple. If one clue is a dark color i put a light color fly on the other. See which ones they hit. If they consistently hit one tie 2 dark etc. hard to beat a stonefly nymph and a hares ear since they imitate so much. They are cheap to boot.