If you intend to master your songs, you should mix with that in mind. Following these steps will make the mastering engineer's job easier (even if that's you) and ultimately give you a better end product.
1) Don't Over-EQ. It's better to have a dull master mix than one that's either too bright or too bass heavy since it's usually easier to brighten things up or add bottom than it is to remove too much of any frequency. Plus, mastering EQs may sound better than what you have available during mixing. If you have to use too much EQ during mastering, maybe you should consider remixing.
2) Don't Over-compress. If you squash your mix too hard, you won't leave anything to work with during mastering.
3) Watch Your Fades. A lot of mixes have some real ragged fades because the mixer didn't listen at a loud enough level down at the end of the fade. A good mastering engineer (even if that means you) will have to fix a fade that isn't smooth later.
4) Do Alternate Mixes. This can turn into a long discussion, since alternate mixes have gotten out of hand these days (with some labels asking for vocal up 1dB, down 1dB, solo up 1 and down 1, background vocals up 1 and down 1, and on and on), but we'll keep it to something simple here. It's best to do at least one alternative mix just in case there's a glitch on your master. And a TV Track (a mix without a lead vocal or instrument) is always ideal for seamlessly removing swear words for a clean mix.
5) Check Your Phase. Make sure that your track plays well in mono by checking your mix in mono. If your lead vocal suddenly drops out, you have a phase problem and you should go back to your mix and fix it. Mono is still an important format to consider in that you'll never know when someone will inadvertently change your nice stereo mix to a single mono channel.
6) Document Everything! It's really easy to forget things like which file is the correct mix and what changes you've made or need (especially after some time has passed) so the best thing is to always have hard and soft copy documentation available.
Next post, more from Remix Hotel.