In the bass tourney world, they have practice days where the fishermen try to locate fish. Relying upon info from their electronic equipment and knowledge they use lure that cover lots of water at the various levels to find the fish. That is what a search fly should do in my mind. Some of the most productive flies in this area are attractor, Rainbow Warriors, Blue Assassins, Lightning Bugs, (lots of flash and non-traditional colors) which I would use as searching flies on streams and lakes I was not familiar with.
"Patriotism supporting your country all of the time and and your government when it deserves it"- Mark Twain