Set up the band's equipment in a suitable space where you will not cause disturbance to neighbors. Set up your home computer and recording software. Connect the audio interface to the computer. Plug your microphones into your audio interface. Set up mics in front of each amplifier. For drums, use one mic in front of the kick drum, one over the snare and an overhead mic to capture cymbals and the rest of the kit.
Record each musician's part. You may opt to record each part separately, or all together. How many tracks you are able to record simultaneously depends upon how many inputs your pre-amplifier/audio interface has. During each take, monitor the recording levels. If an instrument clips (goes "into the red" on its on-screen meter), stop the take. Reduce the level of pre-amplification gain for that instrument on the audio interface before starting a new take. Listen to each finished track separately, checking for audio glitches and mistakes. Re-record any parts that are not of an acceptable standard.
Mute all parts and then un-mute them one by one. In the example of a garage guitar band, un-mute the bass drum mic first, then the snare, the overhead, the bass guitar, the electric guitar and finally the vocal. Set the volume level of each track so that it is audible enough, but does not drown out the others. Do not set the volume of any individual track to a level above 0dB.
Use your recording software's automation function to turn up or down the individual tracks at points where they are not loud enough, or peak dramatically. Use EQ plug-ins in a complimentary way, toning down high-end frequencies on bassy instruments and the lowest frequencies on instruments in the treble register. Aim to prevent "masking," the phenomenon where instruments inhabiting the same frequency space clash with each other and cause a muddy, unclear sound.
Take 24 hours without listening to your "finished mix," then go back and listen to it again with fresh ears. Burn a CD copy and listen to it on as wide a range of audio systems as you can. Write down any problems you can discern with your mix. Make any necessary adjustments to the mix. Share the song with the musicians and friends to get opinions on how it sounds.