With this method, you'll usually feel a fish strike. Most of the time you want the nymph to drift close to the bottom and many nymphs are weighted to help them get there. You can also add a small splitshot sinker. But just before the hatch, when nymphs are swimming to the surface, you should use unweighted nymphs and fish them higher in the water column. Popular nymph patterns include the Gold-Ribbed Hare's Ear, Zug Bug, Damselfly Nymph, Pheasant Tail, and Brassie.
Some streamers imitate other organisms, including large nymphs, hellgrammites, and leaches.
In any case, streamers are a good choice when there is no hatch. Most fish will take on the swing, and it's a good idea to vary the speed of the swinging fly to figure out what speed is most productive. To slow the swing, cast at more of a downstream angle and let out line as the fly starts swinging. To speed it, cast almost strait across and strip line as the fly swings. Large streamer patterns can work very well when fishing at night for big browns.