start the bike and listen to the engine running. Take it really easy at this point, no quick blips of the throttle to warm it up. Once it's warmed up start making passes back and forth at about 1/4 throttle for about 5 to 10 minutes on level ground. I found myself going through a few gears, but only at idle to 1/4 throttle. Try to keep it in 2nd or 3rd and just slowly accelerate and decelerate when needed to turn around etc. no quick revs, nice and smooth. Some will say to let it cool down after this first cycle, some say it doesn't matter. I let mine cool and then on to the next step.
Next, start making passes 1/4 to 1/2 throttle for about 10 to 15 minutes. After this is done, take a look at your bike and make sure everything is still good, listen and make sure it sounds normal. If everything seems ok, go ahead and start making 1/2 to full throttle passes for about 5 minutes. Listen and make sure everything sounds good, there shouldn't be any abnormal sounds or any excessive heat.
The last thing to do, is a so called "super secret magic" part that really makes the bike run great. I found this online, and I'm not sure exactly what it does, but it came from a good source and it really seems to get the bike working better and gets it the right heat etc. to set the rings. On this part you'll still be making 1/2 to full throttle passes, but shift up a couple gears to where your dirt bike is starting to bog even at full throttle. Keep it pinned even while it is bogging and hold it until it cleans up. Do this about 15 times and your done. You'll have better compression and a longer lasting, more reliable top end.