Eh. I never really fly anything with a fancy engine monitor like many of you here, so it's pretty basic as to what can be done.
On the ground after startup I usually lean right away, to the point to where the engine is barely running. When the engine is producing almost NO power, no damage can be done by this. One thing that is fairly important if you are going to do this, lean SO aggressively to where if you applied full power the engine would die. The reason for this is to make sure that you don't have it way lean and then takeoff full power like that, as that could cause damage. So either don't lean at all, or lean to the point to where it barely runs on the ground.
I generally just go full rich for takeoff after that.
On a hot day, a heavy airplane, or a ...very short "runway".. I will lean for peak power before takeoff, It MAY make the difference that might save your @#@$.
Per Lycoming in cruise I generally lean until a slight roughness, and then enrichen until the engine is smooth. (Best Economy)...For I am poor. I'd rather get there slower (build more flight time) and save some money all at the same time.