Posted for W Atkinson <Walter@advancedpilot.com>:

 The process is the same at all altitudes.  Lean until there is a max rise in
rpm and then lean just enough more to get a very slight drop in rpm.
 
 Walter

"""
 While I do not lean agressively, at my altitude in the
 Denver area I definately see a rise in RPM, fuel flow
 drops and the engine idles smoother.  Having said
 that, those of you who adjust mixture for gound
 operations, what process do you use to determine
 mixture settings for elevations above 3000 feet?
"""