From Bob Woodman Tires...
http://www.bobwoodmantires.com/hoostiretip.htm
Tire Break-in Procedure
Proper break-in will not affect initial performance but will increase the competitive life of the tire.
The procedure can be broken down onto phases.
1st phase: The initial run
2nd phase: The length of the time the tire is allowed to "cure"
The initial run
The first laps for the tire are critical for setting up the durability and competitive life. The first session should consist of 10-15 minutes of running. The early part of the session should be run at an easy pace, with the speed gradually increased until the end of the session. The final lap should be run at the fastest possible speed. The intent is to achieve maximum tire temp on the last lap. At this point the car should be brought in and the tires allowed to cool at a normal rate. Optimally, the tires should be removed or have the car jacked up during this cooling.
During this process, the inflation pressure should be 3-5 psi higher than you would normally use. The best progression would have the driver taking 4-7 laps to accomplish this break-in. Each lap should be approximately 7-10 seconds a lap faster than the previous lap. The goal is to have the tire temp as high as possible on the last lap without "shocking" the tire during the warm up laps. In essence, no wheelspin, late braking, or sliding. The last lap should be at, or very close, the maximum possible.
"Cure" Time
After completing the above, the length of time the tire is allowed to set is possibly more important. The barest minimum for this process to be beneficial is 24 hours. (Not "the next day"). Any less than this is a waste of time. The best situation would allow a week before using the tire again.
Proper tire management is a difficult process. To accomplish this almost always requires a second set of wheels. The payoff is greatly increased competitive tire life.