You know your a n00b when-

You know you're a noob when you always play Heavy in TF2.
 
you know you're a noob when you think that the sleep ability in kirby restores your health (like rest in pokemon)
 
MCS said:
You know you're a noob when you think Magikarp is useful.

The only useful things about Magikarp is Flail and it's evolution.
 
You know you're a noob when you spam Special moves in SSBB.