There is even the old school trick of taping two mics together for the vocalist so you can get you're own feed of their performance instead of tapping the board which you'll have no control over. If you watch those ancient live Black Sabbath in Paris vids (that they released an album for) you can see Ozzy has two mics taped together. Not ideal for sure but you get your own feed you can watch and set from you're own board. It also means a shorter cable run if you set yourself up slightly off stage or even onstage instead of relying on bar cabling and the quality of the output the mixing guy tosses you.
 
PS: To anyone trying that... put a piece of felt or rubber or something in between the two mics at any point where the have physical contact with each other and tape them TIGHT together with each other. You don't want ANY grinding or vibration transfer going on because that will be picked up and recorded (and go through the PA).
 
aaaand maybe consider making it so your recording mic is taped a little further down the PA mic so if the singer is a "mic swallower" the PA mic takes the hit. Not your recording mic.

It shouldn't be too hard to get extra mics on a stage if they want the show recorded. The audio end of it a breeze compared to getting good video.
 
The show I recorded, I kid you not, these 2 morons stood in front of the camera pointing out of a window directly behind me. Again, this isn't a small handy cam and these guys knew I was there and what I was doing. I think that kind of douchery will be the biggest problem with this thing.

Bflat5
It shouldn't be too hard to get extra mics on a stage if they want the show recorded. The audio end of it a breeze compared to getting good video.
 
The show I recorded, I kid you not, these 2 morons stood in front of the camera pointing out of a window directly behind me. Again, this isn't a small handy cam and these guys knew I was there and what I was doing. I think that kind of douchery will be the biggest problem with this thing.

And that right there is the WORST part of live video/audio recording. Drunken, clownph8ck douchenozzles who can in an instant destroy an otherwise epic documentation of artistry. You almost need bouncers to specifically keep the drunks away from the gear.
 
A good respectful crowd though adds a lot to such recordings. Delicate balance.

Beepster

Bflat5
It shouldn't be too hard to get extra mics on a stage if they want the show recorded. The audio end of it a breeze compared to getting good video.
 
The show I recorded, I kid you not, these 2 morons stood in front of the camera pointing out of a window directly behind me. Again, this isn't a small handy cam and these guys knew I was there and what I was doing. I think that kind of douchery will be the biggest problem with this thing.

And that right there is the WORST part of live video/audio recording. Drunken, clownph8ck douchenozzles who can in an instant destroy an otherwise epic documentation of artistry. You almost need bouncers to specifically keep the drunks away from the gear.
 
A good respectful crowd though adds a lot to such recordings. Delicate balance.

Or how about the ones that want to apologize for it, but don't realize they're still screwing up by screaming how sorry they are for walking in front of the camera?
 

These days most boards have have usb recording including multitracks AND includes the stereo mixbus out.   Just ask the sound guy in advance if he wouldn't mind capturing the tracks for you.  Bring your external HD  and load it up after the gig.  For me, I like to take the multitracks and mix them and then line it up to the digital video which really is NOT hard.   Here are a few examples.  These tracks were captured from the Behringer X32 and video from a Zoom Q3 HD.
 
https://youtu.be/fT_RwCjD-RA
 
https://youtu.be/Z0ZjH9vi5EA
 
https://youtu.be/g-DmceTyaH8
 
The fact is , as stated numerous times above, MOST stereo board mixes are useless due to the stage levels.    I think mixing multitrack is WAY better but more work but the results are worthwhile for you and the client.
 
NOTE!!  Make sure you or the soundman include an overhead on the drums, even if they don;t put through the system
 
Also, I didn't go crazy on any of these mixes and often you can do a set and forget to get a basic mix that works for everything and then focus on a few songs that the client might want to give extra attention to.
 
Lastly, I mixed the audio in Sonar Platinum and did the video in Vegas 12.  Not sure how well Sonar would have handled the whole sh-bang

I didn't even think about USB outs. Could you connect the board to a laptop via USB and capture each track with Sonar?
 
I'm a Vegas user as well, but haven't upgraded since 10. Is 12 worth the upgrade?

The multi track USB option is rare unless they are using a high end digital mixer or a Behringer X32. USB recording on low end mixers of the type found in night clubs will be only a 2 track which is the same board mix as you get from the RCA type record outs only it's digital. 
 
 

There's a fairly good chance to have FOH using a X32 or likewise. These things sell like crazy ... if you are lucky and this guy got one, however, USB access to all channels is still not plug and play because you need to set up drivers, have a PC that can take up to 32 tracks for the entire show ... and just the channels may not be enough, because you don't have the room coming via the mixer, so you would have to set up a stereo pair of pretty decent microphones, probably right where the mix desk is (because that's where the FOH mixer's ears are) unless it's in a corner somewhere ...
 
I don't think there is good chance for a proper recording unless you get to know venue, band and FOH before the show.
 
If you can't do anything in advance, I'd go there with the stereo pair of pretty decent microphones and place them in the best sounding location which is save from audience interference and just record the stereo signal (mind you there will be a difference between empty club at soundcheck and later when the club is full)... and be nice to FOH so that he creates a great sound for the band and not just gets his job done ...

Whoever said USB out is rare is wrong. Almost every sound company now has a Behringer X 32 admitting mom and many people have smaller mixers that provide USP out now so I think the chances of finding somebody with USB out is probably about 60%. otherwise I agree just get some good front of the house Mike's and also the stereo from the board and between Those tracks you should be able to get a pretty decent live recording. The idea is you need to keep it simple or it will become a nightmare

Nice tips in this thread.
I occasionally record live and its a challenge since there are lots of constraints. e.g I record a choir doing arrangements of some of my wife's music in a local church. While there they have decent reinforcement gear (I got them a pair of Line 6 L3T's - great for easy setup) there is very limited capability to record since I can't set up any intrusive wiring or mics being a church. So I normally just end up placing a couple of field recorders and cameras and hope for the best!
Here is a YouTube video of a song from the most recent event. The recording is not great but it serves the purpose :)
 
A zoom and Edirol R-09 on either side and a Gopro and Sony camera recording video. I did the entire mix in SONAR and video export (Vegas) in about 2 hours yesterday so its pretty rough. Definitely some phase issues but I didn't have time to fine tune.
In SONAR I just fly in the audio tracks and typically use Ozone and prochannel for some tweaks. In this case I cut the bass on the choir mic's since I was getting plenty from the recorder closer to the band. Did some expansion and spatialization in Ozone and finally used the new Max style dial on the master. In Vegas I ended up adding in a small amount of camera audio from the one closed to the choir since it had a bit more definition of the highs.