PG has it right, just be yourself. I actually believe you would be making a mistake acting the way you perceive somebody would want you to act. If they don't like who you are it isn't a fit...I would guess most of the time both sides are looking at and for the same thing anyway.
If you are good enough you will be able to act any damn way you please and someone will over look it, you will be signed but it may limit your choices. All the talk about attitude, bench behavior and the rest is on a sliding scale of talent.