There are always going to be kids who are picked on because they're unattractive, unathletic, don't have their social skills nailed down pat, or they're the new kid on the block. (A good read is .... well, I can't think of the name of the book, but I have it, an it describes in vivid detail groupthink, shunning and teasing among girls.)
There are then kids who ... well, EVERYTHING seems off about them. The way they dress, the way they talk, personal hygeine, everything. It would take more than just advice to help; such children may have Asperger's Syndrome to some degree. Some hardcore computer geeks -- the smelly, pear-shaped, strangely dressed folks you see coding away at midnight in a college computer lab -- have Asperger's.