This is a pretty simple and straightforward nymph. What makes it different is the marabou herl used for the body.
Hook: Mustad 9671 (2XL wet fly), 8-14
Tail: Straight dark hair (moose, horse mane, human hair, etc)
Body: Marabou herl (long)
Wingcase: Wild turkey tail feather slip
Throat: Grouse body plume fibers
Thread: Monocord
If you've ever tied a nymph before, there is nothing here that varies. If you haven't, then refer to a good nymph tying manual. There are many available. Lay down a foundation and cement. Tie in 3 straight tail hairs, then marabou herl. Wrap thread forward to mid-shank. Wrap herl to mid-shank and secure. Tie in turkey tail slip. Wrap thread forward, then continue with herl. A slight taper, thickening toward the eye, is recommended. Tie off, then fold turkey slip forward, tie off and trim excess slip and herl. Tie in grouse fibers for the throat. Finish with a wrap knot. Cement head and wingcase. Allow to dry thoroughly.
The one advantage of this nymph over others it the motionof the body when wet. The marabou fibers of the herl are constantly alive in the water, giving a very good impression of gills. This is one detail that will often trigger a bite when other nymphs won't. Plus, they are relatively inexpensive to tie. They make very good working nymphs, no crying shame when they are snagged on structure. A weed guard is optional for heavy cover.
Fish them much as you would any unweighted nymph, and don't be afraid to let them crawl at a very slow speed.