You need to send a stereo file exported at 44.1Khz (minimum) and 16 bits (minimum), in WAV format.
If your file is recorded at a higher quality, i.e. 48Khz (or higher) and/or 24bits (or higher) much better. This way I will count with a bigger headroom to work. I will dither it down to CD quality once it is mastered.
Do not compress or limit the song.
It's not necessary to remove silences from the begginning or the end of the song.
Do not fade in/out the song, just send a comment if you want fade in or out.