In fly tying I've used both goose and turkey biots in my tying. The goose material is usually a bit stiffer and shorter, while the turkey can be quite long and not so stiff (also not as strong). I use biots for tails on nymphs, i.e.: many stonefly nymphs; prince nymphs, etc. But, where I really like them is as abdomen bodies for both nymphs, emergers and dries. I usually tie them 'fuzzy' for emergers and smooth for most dry flies and/or nymphs.
Here are a few pics:
Tie in fuzzy for emerger abdomen:
Tie in fuzzy for dry fly abdomen:
Tie in smooth for dry fly abdomen:
Tie in as tails and wings on nymphs: (this is one of Charlie Craven's ties and pics)
There you have it. I'm sure there are many more uses for biots, but these seem to be the most common. I wouldn't be without biots and, in a variety of colors, as I consider them a valuable tying material.
To learn how to tie either fuzzy or smooth depends on how you mount and wrap the biot on the hook. There is a notch in the wide end of the single biot where it stripped off of the stem. Usually, notch up (towards hook eye) means fuzzy, notch down means smooth. Another tip to remember is to make sure you soak biots before using them as they tend to be brittle. You can tie them without soaking, but I have much better success when they are a bit more pliable. Last tip, make sure to lay down thread or very sparse dubbing on the hook before wrapping a biot, and use cement under the biot in order to make it durable - nothing worse than a biot coming unwrapped after a few fish because it wasn't glued in place.
Hope this helps. Good luck.