Hey Crew,
Before I practice, since my set is in my garage, and temperatures change a lot up here. (NorCal in the High Sierras) I even tune top and bottom heads, as during some tunes I beat the living hell out of everything, and I can hear the difference when playing softer, more "finessed" songs.
I always tune after setting up at a gig, and check again after the 2nd set.
I have cheapo heads on my rack toms, and those seem to need the most attention. Those are also the heads I've "ironed" the most.(go figger!)
Rock on,
C. P.