The commission process is simple, name your price. If I don't like it, we can negotiate to what you can afford.
Requests are kind of silly in my opinion, asking for one kinda seems like you're implying that the artist's work isn't worth actual money, or at least points... and that they have nothing better to do then use their valuable time to draw something just for you. Um, no. People who take requests have my respect though. o-o
Art trades will be open for friends only (for the most part).