Get an 8GB (or bigger) card for it, don't lose the one that came with it because you'll need it for software upgrades. Turn off any limiter and compression when recording (you can add that later if desired). Set it to record at 24 bit and 44.1 or 48kHz. 24 bit allows you to run a more modest recording level then amplify it later in post production. Higher sampling rates are great but eat up storage space. Those are basics.
Running external mics, positioning the mics, et.c are more detailed topics and specific to certain circumstances. You will want to get the mics into "clear air" and away from unwanted noise. In other words, you want nothing to block the sound between the source and the mics or it may sound muffled and you want the mics away from loud drunks. Investing in a stand or some sort of mounting device helps and keeps you from adding handling noise into the mix. You can get extra gear as needed along the way. Check the "Yard Sale" here for some great deals on quality used gear.
You'll need an audio editing program. Audacity is free and works. Other people prefer other apps, some really cheap, some not.
Read, experiment, read some more, try again. Don't get discouraged. Ask questions here when they come up.
One other factor, does the band want to be recorded? Some do, some don't. Asking is the polite way to go but some bands are known to be ok with it. Others are known to not be taper friendly. The venue also has a say in taping.