To prepare a song for mixing, you will need to bounce out all of the tracks within your project, all starting from the same point. Bounce to WAV or AIFF, 16 or 24bit. For vocal tracks - make sure you have taken off all plug-ins and effects before bouncing - the vocal files you send me should be completely raw with no processing. If I am mixing your instrumental, leave your channel plug-ins and effects on, as these usually shape the sound of your beat. Be sure to take off any master bus/stereo output plug-ins before bouncing.
For mastering, you will need to bounce/export a mixdown of your full song in WAV or AIFF (16 or 24bit). Be sure to take off any stereo bus/master bus plug-ins prior to bouncing.
IMPORTANT: Ensure there is no clipping on any of your tracks before bouncing. Your meters should not be in the red, as this can result in nasty digital distortion. If you notice any clipping/red on your meters, please turn your channels down and check again.