writing is not a visual medium, and trying to paint someone's appearance as clearly as a photograph or illustration is unwise. Do mention anything notable, from hair color, length, scars, eye color, etc. Anything that needs to be kept consistent from post to post. In books, a lot of writers simply give you the character's name and let the reader imagine them however they desire. The only time it really becomes nessisary to know exactly what a part of a character looks like is when it's important to the story. Such events include everything from an individual who's looking for long haired girls, or maybe if your character has long or short sleeves in the event someone tries to grab them. 

I find the more interesting aspects of describing something is writing it's history instead of how an item or person looks. Don't describe how the scars on a warior's face look, explain how he got them. As I've said in other topics, quirks in the character's behavior are more interesting than their appearance. Anyone can have a fancy sword or a unique body alteration. But how many characters do you know that smack their cheeks when they wake up in the morning? collect pave stones from the roads they walk on?