You can be replaced, but usually not til you've done a LOT of damage. When your character isn't talking, mug. For a touch of realism, upstage yourself. Give fellow actors advice on how to do their characters. If you can't get a grasp of your character, just do Jack Nicholson .
Eye contact is for actors afraid to stand on their own.
Blocking is for amateurs. Change your blocking on opening night. It's not the quality of the role, it's what you get to wear. Wear all black and hang out in coffee houses. Break a leg.