1. Make sure that there are no FX on your Master Bus when bounce or Export!
2. Make sure that the level of your track peaks somewhere between -6 and -3dB.
3. If The Peak Level of your track is higher then -3dB, it is best to reduce each tracks level rather then to just drop the master fader.
4. Eliminate any unwanted noise within your mix.
5. Try to keep your mix clean and dynamic.
6. Leave some silence at the beginning and at the end of your track (2-8 Bars).
7. Bounce your track in the format you worked in.
8. Be sure NOT to normalize, or to apply any dither when you bounce or export.
9. Think about the Realisitc and Relevant reference tracks that you might be able to suggest to your mastering engineer.