1 Bit depth, sample rate, and file type

Most people are mixing in-the-box these days or at least printing mixes back into their multitrack session after analogue summing/processing.

Always send 24 bit mixes to mastering. This maintains the maximum resolution of your mix. Even a 16 bit project mixed in-the-box benefits from a 24 bit bounce. 32 bit files can present compatibility problems with some systems, and must be down-converted to 24 bits before analogue conversion.
DO NOT CHANGE YOUR SAMPLE RATE. There is no benefit to upsampling a printed mix. Also, if the sample rate for your project is higher than your ultimate release format (you recorded at 96 kHz and are releasing a cd at 44.1 kHz) let the mastering house handle this conversion.
Don’t downsample your mix!

For reasons of compatibility, send your mixes as stereo WAV or AIFF files. Don’t send SDII files (an older Mac-only format). Don’t send MP3’s, M4a’s, or other compressed formats.

2 Processing on the master output

With the abundance and variety of plug-ins these days, it’s tempting to process everything beyond recognition – even the stereo buss!
Resist this temptation as much as possible. Plug-ins are great creative tools, but use them judiciously. Trust your ears and don’t be seduced by fancy GUI’s.

I’m not going to tell you that you should absolutely-under-no-circumstance use plug-ins on your master fader.
That’s not good advice. Sometimes a mix needs some compression to make it work musically. Without the compressor, the mix no longer makes sense in. However, if you have even the slightest doubt, just print an alternate mix without the plug-in. That was easy!

As far as other types of plug-ins go, I would shy away from a master eq – rather address any frequency problems on the individual tracks.
Also, (and this should go without saying) don’t use maximizer or
limiter plug-ins just to bump up the level or prevent clipping. The
mastering engineer will take care of getting your mix loud (if that’s what you desire). If your mix is clipping the master output, just turn it down.

3 Master output level

A lot of people get hung up about having a specific peak value to their mix. I don’t think that having exactly 3 dB of headroom will make or break your mix. As long as the peaks aren’t clipping and the mix isn’t printed super low, I’m a happy guy.

Generally, I advise people to mix so that their RMS level sits somewhere around halfway up the DAW meter. This leaves plenty of room for peaks while keeping the body of the mix at a decent level. If you find that your mix is clipping the master output, turn down that master fader! DO NOT USE A LIMITER TO STOP CLIPPING.

4 Take your time, love your mix

This seems so obvious, but gets overlooked so often. You don’t need to be the world’s greatest mixer to get a great mix; just take your time.

Not working in the greatest listening environment? Just burn a copy and check it out in your car or home. Do this enough and you’ll figure out what works for you. If you’re still unsure, ask your friends. There are even “check out my mix” groups on facebook.

You might even ask your Mastering Engineer for a mix critique in advance of your mastering session. I’m happy to provide these for free as they make my job easier!

5 Stems

This method of mixing/mastering is becoming more and more common.
Once you have achieved what you think is your final mix, bounce stereo submixes of the various components. Drums, bass, guitars, keyboards, lead vocals, bg vocals – whatever you want to keep individual control over. Ensure that all submixes have the same starting point.

The Mastering Engineer can then drag all of the submixes (stems) into his/her DAW and play back your mix with the ability to change individual elements. This is the ultimate for the non-committal set.
Just keep in mind that you may be asking you Mastering Engineer to do a bit of mixing. Additional costs usually apply.