As much as I'd like to say that there's no right or wrong way to describe a character, writing "she had flowy blonde hair, sparkling blue eyes, a button nose," etc, etc, and then proceeding with what she wore in minute detail seems overly Mary Sue-y and amateurish. Unless it's extremely vital that we know these things (is it ever?).
I do have my own particular weakness, which is hair. If I don't get to describe anything else about my character, then at least let me describe the hair! (An example: my current WIP begins with a character playing with their hair.) But I like thinking of roundabout ways of describing things. For example, instead of saying a character has long hair, I get another character to tell them that she/he/xe is overdue for a haircut.
Writing and reading/doing crit for screenplays, I've found the rule of three is golden. You basically want to use as few words as possible to convey the character as quickly as possible. Something like: "Charlie [Sixteen, spotty, compulsive gamer]", gives me a good idea of what Charlie's like. I don't have to know everything about him, I've already built an image in my head. I try to keep that in mind.