if its a river, trout lie in particular areas in the flow. They don,t move to far, as food comes to them on the current, so just watch for a while and they will give them selves away. On still waters like dams, resivoirs, trout have to keep swimming to pass water over there gills, so they dont stay in one area. Certain areas will hold fish more than others, such as sunken roads, hedges, drop off ect, but the wind plays a big prt on still waters. It may be blowing flies onto the water or pushing rising pupae to another shore. Most of all you have to use your eyes and learn about the water your