I typically use a great little AT3030 mic (discontinued, however, but you can find a similar mic), positioned on the side of the hat away from the drummer and snare, facing almost straight down on the top of the hat (about 3-6 inches from the
raised hi-hat level), about 1" from the edge. The hi-hat itself blocks out the snare, and by facing the mic downward, it reduces bleed from other cymbals. There is nothing else I find this mic needs to pick up.
I may adjust the angle of the mic to pick up a little more of the bell of the hi-hat, but I usually won't move the mic.
So, in essence, I will try to "hide" the diaphragm of the small condenser hi-hat mic from the rest of the kit where possible. In most cases, unless you're really adamant about picking up very subtle stick hits, this is my recommendation.
George Massenberg discovered a unique way of dealing with this as well, by placing a ribbon mic between the snare and the hi-hat. Through the front of the mic, he picks up the side of the snare, while the back of the mic, usually the brighter side, picks up the snare. The hi-hat side will cancel out the snare side. I haven't tried this yet, but the video is here.
http://www.youtube.com/watch?v=OZOVZQgXl9k