Sean,
What you really want is the pattern on the pavement; the lower the pressure, the more likely you will have 2 rubber tracks at the width of the tires; the higher the pressure, the more likely you will have 1 rubber track, but not the complete width of the tires. Do some burn outs, and set the pressure to give the tire track that is closest to the full width of the tire. Then lower the pressure but be sure to maintain a contact patch that is full width. Remember, the bigger the contact patch, the more the tire is giving you traction. If the contact patch is light in the center, put in more air; light on the edges, let out some air. As you heat the tires, the pressure will increase, and the effects mentioned above will come in to play.