Originally Posted by MDV
This, so much.
I think there are two questions here - one, how best to get a project to a particular mastering engineer, and two, general things to think about while mixing, knowing that mastering will happen down the road.
The first question needs to be answered in conversation with the guy you hire.
The second more general question, you're on the right track - it's not uncommon to, as you get towards the end of a mix, throw a couple compressors and a limiter on the master bus coupled with make-up gain adjustements, to simulate getting another 5-6db out of the mix using compression and make up gain just to hear what happens to it once you start to compress the overall mix. Of course, you need to remember to turn these OFF when you mix down, and it's usually helpful to subsequently tell your ME what you were running through on your master bus at this stage just so he has some idea what you were hearing.
But, for now, most of getting a mix ready for mastering is just making the mix absolutely kick ass.