I have a few wigs, and I most certainly destroyed my first one. All of mine are costume wigs from hollowen stores, but if you pick a good cut, right color, and have a little luck, they can be quite passable.
Ok, a few do-nots from personal experience(just realized you didnt mention, but all this info is for synthetic wigs):
Don't use a standard comb or brush, wide toothed combs are OK, but really unless you slept in it (don't

), you can use your fingers. Comb your fingers thrugh, lightly bouncing through any slight tangles. Remember, stretching the hair(or heat) will frizz it up like crazy.
Don't use product intended for normal hair, cleaning is done in a gentle bath of light soap with a wrinse, conditioning should he done with a wig-specific conditioner. If I recall, the Wiki here has more detailed information available. Although, ill admit, with the light use my wigs get, I haven't cleaned em (since the first one) but I do detangle everytime.
Yes, I killed my first wig by combing standard leave in conditioner into it. There, you, happy? I said it. Lol (the conditioner made it kinda sticky, and the dirt just loved it, plus, the combing stretched the hair, making friz, which makes tangles....... it was rough.)