The way that I am doing it, I purchased the Tascam 1800, gives me 16 inputs (two through a SPDIF preamp). The new Tascam drops the SPDIF which is better. Put it all in a Gator rack case, added a rack power strip and was set for sound.
Purchased a drum 7 piece mic kit (I suggest 4, kick, snare OH's) Mic the guitar amps and bass (in case you want to do more than acoustic), vocals, depending on the mixer, I split the dynamic Mics, but if you have another way of getting the vocals from the mixer that is better. If I have any inputs left, mic the room in case I want to add flavor.
Purchased a cheap laptop and Reaper, and just track while mobile. Mix when I get home. Very little processing required on the portable sound system, therefore, I beefy laptop is not required. That setup is pretty flexible. 16 inputs/channels is 99% as much as many of us would need here.
Here is what I learned along the way. First, setup takes a long time. I had 7 on the drums, but really the OH's take care of the Toms Kick and Snare mics gives you ability to add punch. I have to say the 4 mic drum recording is worth considering. Also, keep the bass away from the snare. One of the bands I recorded, the snare rattled so much, I couldn't mix it. Lessons learned.
Getting the vocals in seems to be the hard part. If you can get it straight from the board, then you can set the level so it doesn't clip and just get it to mix later.
Acoustic is rather hard because the guy I recorded wanted to move around a lot. I tried to do a combo Di and condenser mic, but his pick up he insisted on over driving and it sounded like crap. The condenser was really inconsistent. Required a lot of post wave editing to get the levels consistent.
The last thing is, these guys sucked and when I recorded them, it showed how much they sucked. You get away with a lot of stuff playing live, once it is recorded, all bets are off. Make sure the band is well rehearsed or you will not enjoy the journey. When you play in the studio, usually everything is isolated, somebody screws up, go do it it again, punch in, make some tweaks. Live, the bleed reduces what can be fixed. So, what you record is what you get when recording a real live session.
The others will have better tips, but I think the above at least gives you some basics.