Regardless of the break in procedure you use (2 minute runs, 1 minute runs, etc..etc..) the most important thing is to get your engine to operating temperature (about 225 degrees F) as quickly as possible. Full throttle operation at a mixture setting just past the 4-2 stroke point will get you there. After this, some people recommend long runs at this setting, some recommend short runs with cooldowns, some recommend short runs with smaller props)