Getting ready for a live recording is just like getting ready for a studio session. Lots of rehearsals will get the musicians ready to perform at their best. If they do 6 or more shows per month as a group, this won’t be too difficult – unless new material is going to be performed. New material would require more rehearsal time. If the group performs sporadically, more practices might be necessary.
Everybody’s gear needs to be in its best condition as well. New drumheads, new strings on any stringed instruments, and spares on hand for anything that might break. It would be best to put the new strings on the night before so they can stretch out overnight. We’re about to put some amazing sounding mics (connected to some killer mic pre-amps,) in front of, or next to, your instruments. You don’t want to end up with an incredibly accurate recording of a bad sounding instrument.
While we’re at it, make sure everybody is rested, and as stress-free as possible. Don’t schedule a live recording on a Tuesday night when one musician has to slip out of work early and battle rush hour traffic to barely make it to the gig on time. An ideal situation would be to perform at the same venue on consecutive days/nights. You can get multiple versions of each song with near identical sounds, providing the best opportunity for easy editing.