If I was recording a song should I record tracks in mono or stereo, what do most people do, and what are the advantages of doing either...

From N-Track Wiki

It depends on what instrument you are recording. For most purposes a mono recording is most appropriated as for voice, guitars. If you are recording through a multieffect device, maybe you should record in stereo, as such device will enhance a mono sound outputting it in stereo. Also if you record the single tracks in mono, the final result will be always a stereo song: you can pan each track more in one channel or to the other.