Well, that's something that alot of people like to debate. I don't know what's best and i'm not going to claim what I do is the best because someone will want to argue.
All I will say is, this is what I use: http://cefx.net/catalog/breakin.php Just so you know, you will have a decent amount of pinch left doing this method. I also had an engine expert look at my motor after break-in and he said whatever method I used is a good one because the motor looked like it had been broken in right, in his opinion and he didn't know what method I used. This method seems to be pretty popular and I haven't heard anyone say that they didn't like it. Doesn't mean someone out there doesn't though...

If you want hardly any pinch left after break-in, use Mike Swauger's method. He posted it on rctech somewhere and I used it on my plus 12 and that motor has been really good to me. But, I think it's getting worn out a little too fast and it might need a piston/sleeve soon. Hope that helps.
Paul