I would love any wisdom regarding preparing a record (12 songs) to be sent to be mastered. I'm sure I will get instructions from the mastering house, but wondered if anybody has done this prep with Sonar Plat.  I'm aware that I could master it myself but am choosing not to go that route.
 
thanks.

Make sure each of your songs has sufficient headroom - I'd suggest anywhere from -12dB to -6dB
 
Try to make sure they are all of a similar loudness, but don't sweat it too much as the mastering guys will do this routinely
 
If you have a specific track order in mind, make sure they are aware of this.

ask your mastering engineer how s/he prefers you to deliver - format, etc

Thanks guys. SO...to give my tracks sufficient headroom, I would remove all compression/limiters from the Master output and then just lower the master output volume?

Remove any Fx from the Master Buss yes.
 
I would NOT lower the MB faders - leave them at 0dB

Bristol_Jonesey
Remove any Fx from the Master Buss yes.
 
I would NOT lower the MB faders - leave them at 0dB

What if you have a reverb on the Master Buss? I can see "maybe" taking off a compressor but why remove an effect that is part of the song? Or am I crazy for putting a verb on the master? Seems like a good place for a tying reverb to put everything in the same space.

Well, I always put reverbs on their own reverb buss(es) - which then goes to the Master
 
When I said "remove any Master buss Fx" I was referring to any sort of mastering chain the OP might have set up

Remember the more you put into your project, the more you will get in return.
Typically anything I master, or in the past when I have sent to be mastered, I not only send the tracks but also a document for each track with an instrument list (letting them know how many tracks were on the mix, instrument type,exc) and also Producers notes that pertain to each individual song and also all the songs as a whole.
you may realize some last minute things, those should be jot down and sent in the mastering notes.
 
I agree with BJ, I don't use any FX on the master bus (compression, limiter, delay or reverb) remove them before export. I don't let anything above -4dB on that master bus.
 
Remember, don't go crazy with compression and squash all your tracks. its okay for some of them as an effect, but let the mastering engineer reduce the dynamic range with compression and limiting.
of course you need to use compression to tame vocals, round off bass lines, exc but a good mastering engineer will always tell you " don't send me an over compressed mix" because then I have no where to go with it.
 

A good mastering engineer will interact with you about the sound you want. There are at least a dozen valid ways to master a song, but the only one that's truly valid is the one the artist likes.
 
You do not want to put FX in the master bus, mastering engineers should have better toys than you do . There have been occasions when I've added a touch of reverb to a master, although that's very rare. However, I've always found it helpful when I receive a mix with any bus effects in place that someone used so I get an idea of what they want, along with the "naked" mix that I actually master. 
 
I usually give clients a few choices of masters to save time going back and forth to make changes. For example when a client wants one squashed for maximum loudness, I'll do that (I have some semi-proprietary techniques loudness without compromising dynamics excessively) but I also do a version that "breathes" and has some dynamic range. Most of the time clients choose the latter.
 
 

+1  to leaving the master buss clean. Adding anything to the master buss is an attempt to master yourself. Just leave headroom, as said, with no overs. 
You job is to mix. 
Focus on balancing the tracks the way you like it. And try to get the Bass and Kick under control. Easier to get this right in mixing than in mastering. 
Get you overall vibe happening. 
Try and keep it clean and clear.
 
 
Reverb on the master??? well I guess if it is a monks chanting sort of thing.. 
Nothing worse than reverb on bass IMHO.