The best way to improve the overall roleplay on the server is to express excellence in one's own serverside RP, consistantly and regardless of conditions. The second best way to improve overall roleplay on the server is to tutor other players, especially new players, through pairing with them in groups or inviting them into a faction.
EDIT: Also, can I get the customary 'yalalala, disco's dead, all hail the lich king, fix cruise, ect.' out of the way right now? Thanks. I've had my fill of that particular dish today.