I make an effort to be completely set up at least a half hour b4 down beat, which includes allowing the bass to acclimate to the room.* Then, using the bass's assigned clip-on(each has its own D'Addario NS Micro), I tune up. I usually check again after each break. Occasionally needs a tweak or two.
*all our gigs are load-in/out, can't set up "early", no opportunity for empty room sound check, our PA, no sound man other than us
Oh yeah, I think to get really get in pitch everyone should use the same tuner which of course no one does, at least at the club level. I play with a guy here who accidentally had his tuner down 4 cents, it used to drive me nuts after we'd tune up, he was always flat and I would have to tune down to him by ear, one day I said 'gimme that thing' and realized it.
