Preparation
Loudness
Please leave headroom in your mixes! If there is one thing that will hinder the job of the mastering engineer it is a mix that is peaking at 0dbfs. Please don’t allow your mixes to peak any higher than -6dbfs. I understand you want your songs louder than any other song on the planet. Having a loud track is achievable, but don’t try making your tracks loud in the mixing stage. Focus on balance and musicality, but leave the loudness to the mastering engineer. Avoid compression if the sole purpose of its use it to make your mix loud.
Stereo Imaging Plugins
So you want a huge, loud, and wide mix? Doesn’t everyone? Stereo imaging plugins can be great to use on individual tracks or for use as effects, but please don’t use them on the whole mix. If you are absolutely married to the sound of a stereo imaging plugin across your mix please send in two versions of the track...one with and one without the plugin.