While every stream and lake has it nuances and every day can be quite a different day, there are a few fly patterns which work well pretty much all year long around in the Eastern Sierras. While there are many factors in this, simply put, a few fly patterns simply work reasonable well on most any water on most any day. It's generally a good idea to check a hatch chart before heading out as that will help you dial not just the fly pattern, but the color and size. Here's a few to consider for your Eastern Sierra Fly Box:
Of course, you could just stop by your local fly shop and ask them what's working for where you are going.. and purchase from them whatever they recommend.