Our first choice, where possible, is to set up the drum kit on the front of the stage (on stage right, but left if necessary). Guitar rig (1 combo amp) in the middle, about ten feet behind the front-and-centre. Position bass rig (with DI, of course) 6 to 10 feet behind bassist vocal mic stand position. Vocal mics for all three musicians.
If the stage does not allow for a drum kit to be at the front of the stage, position drums on drum riser, guitar rig on stage right (right-hand side if onstage, facing the audience), bass rig stage left. Power supply: 1 for bass rig, 1 for guitar amp, and 1 for guitar effects (at guitarist's vocal mic position). 1 monitor for each of the 3 players (i.e.: 3 monitors total).