Drift fishing, bottom fishing, suspended, trolling and using lures tipped with bait are methods of catching rainbow trout with natural bait. Bait includes live or natural food sources that are usually part of a trout's traditional diet.
Trout are a predator fish and they devour a wide variety of natural baits (and a few that aren't quite as natural). The taste and smell of bait provides the attraction. Baits that attract trout include nightcrawlers, meal worms, salmon eggs, red worms and shrimp. Unnatural baits that can be very effective include marshmallows and artificial baits that are made of scented plastic or paste materials.
The techniques used depend on whether you are fishing in a lake or a flowing body of water, such as a river or stream. For moving water, drift fishing usually works best. Use a small hook and enough weight to partially counter the current and allow the bait to sink but still move with the flow. This works with any bait. Simply cast it upstream and allow it to drift downstream and repeat.
Lake fishing involves casting the rig out and letting it sit on the bottom or attaching a float to keep it suspended. For bottom fishing, marshmallows work well because they float up off of the bottom. If you have a boat, you can troll with a nightcrawler attached to a spinner rig called a cowbell. Small jigs can be tipped with bait for added effectiveness.