If you went fly fishing for Golden Trout in Yosemite on the first weekend of October and there was a recent October Caddis hatch on the small creek you are fishing, that would more than likely be your go to fly for that trip and that entire weekend. Now if you went back to that same creek in May to catch a few more Goldens, you would find that they might be only eating Green Drakes or Stoneflies. This is where many new anglers get overwhelmed in fly shops and as they try to match the hatch on the water. There is no need to take off your lab coat and go back to "Chuck and Reel" fishing, just try and simplify your selection and fine tune your cast.
You will catch more trout over the course of your life with the wrong fly, that is the wrong size and color, but presented with a high quality cast; then you will with the right fly, that is the right size and color, but you had a poor cast. When you're just starting, focus more on your cast and how your presenting your fly to an awaiting trout and not as much on what tiny details of your fly are going to make a difference.
If your getting frustrated with fly selection, it might be time to simplify your fly box and give our list a shot. Pick two different colors and 2 different sizes, but only 4 main dry fly patterns(Stimulator, Royal Wulff, Caddis, and Adams), 4 beaded nymph patterns(Hairs Ear, Stonefly, Pheasant Tail and San Juan Worm), 1 soft hackle(Partridge Hackle), 2 wooly buggers(Black and Olive) and 2 terrestrials(Grasshopper and Black Ant).
Keep your lab coat on but leave your beakers at home when you head to the fly shop next time and try the above list and see what kind of results you have. Remember, cast the wrong fly but with great presentation and forget about the "perfect fly" that you keep casting with poor presentation and let us know about the outcome.
As always, catch the beauty of today!
Yosemite Fly Fishing Guide