place in the top 3 of a contest and or the mods give u one cuz they think ur cool or sum shit idk
It's not only top three, most only give awards to first place.
Opening Post: Another way is to win a RP Tournament (if an award is available as a prize) or receive one from an administrator who believes you have did exceptional work for the site (Normally given to moderators).
If you should browse through the Awards list, you would see some other awards, such as NarutoBase Bug, Best Sensei, Member of the month etc. (Aren't really issued anymore)