My airplanes checklist tells you to lean on the ground immediately after starting - it says an inch (its a PA28-181).
In the air I lean at 2000ft and up - in my EGT I run hottest at around 1480 - it leaned all the way to get the peak then backed off/enriched (my airplane has a carb not injection so none of that lean of peak BS for me!) - when this is done at 8000ft+ the mixture is maybe 1/2" inch off the lean cut off position, v.scary.