Devil's advocate here - it doesn't hurt to have someone elses ears on the material when it comes to mastering, especially if it's getting airplay.
The other distiguished DUC member responses above are all good if you are DIY. I'd like to add that, you take those 3 songs (or whatever) and, if nothing else for comparisons sake, have them mastered by a real mastering engineer. You also get the benefit of being able to compare 'notes' with a pro.
You can have a mastering guy like Rodney Mills (amoung other great engineers) run it thru all the killer mastering gear, and most importantly, run it by his seriously experienced ears. And I know Rodney (
www.rodneymills.com) does it for, like, $10 per final mastered minute of music...thats only $40 bucks for a 4 minute song. You can email him SDII L/R files too!! That's a bargain in my book. IMHO it's that final polish that can take a home job to a world-class sounding record.
Anyway take a gander at the idea, maybe do it just for comparison's sake to see how your version stacks up.
jho