These ideal spots are known as holding lies. Although several fish can be found in one of these lies, the biggest fish will generally hold the best spot in the lie. Each stream or river will be different but there are some general stream characteristics that will hold fish in almost any river. These characteristics are riffles, runs, pools and flats. These should be recognized and fished by all fishermen.
Riffles are fast, shallow and choppy parts of the stream.
The faster water hitting rocks creates them. The rocks obstruct the current creating a pocket of slower water. Runs are the slower section of water that are usually below the riffles. Runs are what fisherman refers to as classic dry fly water. Runs are usually about 4 feet deep and much easier to wade then the riffles.