The "best way" will also be determined by the aircraft having an Exhaust Gas Temp (EGT) guage. If you have one of these, you'll be able to lean much more precisely. If not, you're limited to using the old "lean until you get a rise in RPM and make it slightly rich from there" method.

Also, don't pull on the mixture, unscrew it. When it comes time to go full rich again, you can push in.

Normally, you'll lean after reaching cruise and setting cruise power. Now, if you're at a high altitude airport on a hot day (=high density altitude) it may be nesessary to lean for best power before taking off.