No matter how great of an angler you are, there will come a time where you will struggle to select a fly. It is the ultimate equalizer. And as the old saying goes, you can not catch fish if your line is not in the water. Staring into your fly box as if it is a black hole is not a good place to start. The problem is that if you ask ten different anglers what fly you should use, you are likely to get ten different answers. And this blog will not give you a definitive answers, but it can help to point you in the right direction.
The key to answering this question is done the night before. There are no certainties in fishing, so bring more than the fly you are confident will catch fish. Even the hungriest trevally can snuff the wrong fly. Cover your colors as well as patterns. The first thing I do is start with the pattern and color that I think will work. If blind casting I give myself 15 to 20 minutes of fishing. If this fly does not work I put on a fly with the opposite color. So if I am fishing a white fly, I put on a black fly. Keep in mind, this is what I do when I have no clue what fly to pick. If you see fish feeding on a certain color baitfish, it is probably a good idea to put a fly with similar colors on.
I brought extra orange flies on a trip to Cuba after hearing from reliable sources that the fish like this color. If all else failed, I would put on an orange fly and then cycle through patterns opposed to colors. It worked. I put all of my faith into these orange flies because it was all I had to go off of at times. My boat partner joked about this decision making. I told him I like to put on the fly I am the most confident with because I will cast and retrieve it with confidence. Again he joked about this decision. 
We approached some tarpon crushing baitfish along the beach. We took turns throwing a variety of flies at them. The Cuban guide eventually shrugged his shoulders and said, “I don’t know what they eat.”
My boat partner said I know exactly what they want, and pulled out his favorite fly. I watched his cast improve. He retrieved his fly with joy rather than desperation. The fish did not eat and we moved on. Hours later we encountered the same situation, and my boat partner chose his same white fly. A huge flash of silver came up from the dark. “I told you this was the fly.”
It could have been any fly that day. We had no idea what the fish were feeding on. But if you do not have an educated opinion in what fly to throw, trust your gut. At some point in time we will all end up in this situation. Fishing new places brings us down a few rungs on the ladder for this reason. Trust your gut and tie on what looks and feels good. If that does not work, work your way through the box. At the end of the day, it is just fishing, you have done this before and will likely do it again.
For more resources on fly tying visit:
239 Flies, Flyfishbonehead, Frankenfly, In the Riffle, DronsWorld
