Allow 5 seconds of silence at the beginning and the end of your song.
Don't use effects (Compressor, EQ or others) on the mixbus!
The headroom of your recordings should be 2 - 4 dB.
Mixdown your session in the same format you recorded it in.
Don´t use dithering in the mixdown. Dithering has to be the very last step in mastering!
More about dithering: Digital Domain / Bob Katz (http://www.digido.com/bob-katz/dither.html)
Think about different mixdowns: Vocal up/Vocal down mix (+/- 0,5 bis 1 dB),
instrumental-mixdown, vocal-mixdown, live-mixdown
Don't edit your mixdown! Don't use normalization! If possible, don't fade in or out, we will do it in the mastering.
Soundfiles should be named as follows : tracknumber, name, suffix
(i.e."01_NAME.wav")