Last weekend, we just finished the APS seminar in Kortrijk.
John Deakin was one of the teachers. You can search for his columns on engine management under 'Pelican's Perch'. There is very good information there, even for advanced pilots.
If you lean on the ground (highly recommended) you should lean far enough that there is no chance the engine will develop any more power without stumbling. There will be no chance that you take-off with just a little bit leaning (detrimental). You can lean at any altitude in cruise. At high power and when taking-off be sure to be rich enough.