1. The better the mix, the better the master!
Make sure you are happy with the results BEFORE mastering!
2. Leave mix bus limiters OFF:
Make sure there is a couple of dB's of true peak headroom!
3. If your mix relies heavily on mix bus processing:
By all means keep it on! It's part of the mix and your sound.
4. In case you're unsure of any mix bus processing:
I'd suggest to render two files: one with the processing ON and
the other with the processing OFF. Limiters OFF either way.
5. Sample rate & bit depth:
Keep them as whatever the material was recorded/mixed at.
6. File format:
Mastering is usually done from a stereo wav file.
I don't offer surround mastering. Stem masters can be done in special cases.
7. Tops & tails:
Leave a couple of seconds of empty space before and after the mix itself.
Artist, album & song names: Double-check for errors.
The order of the songs on an album: "01 Kickass Intro", "02 THE HIT", "03 My Favourite Song" etc.
Specifics on the assembly of an album: Track pauses, fades etc. (if any)
ISRC codes: If available.
Release platform: Digital? CD? Vinyl?
Specials & Keywords: Wishes on tonal characteristics / reference tracks
/ Expectations when it comes to mastering
Payment details: Name, address, VAT etc.
Contact e-mail: To which invoice and master file downloads can be sent.
If anything should come up, please do not hesitate to ask.
..and don't overthink it! :)