With mastering there are things. I like the Infected Mushroom's newest stuff their mastering is pretty tits as far as I am concerned, but that's becuase it's what i like.
Mastering is damn subjective. Once again, you like what you like. If it sounds good, great, if you have a song you are modeling another after then you have a good place to start. For instance:
I modeled something I did recently after a song by Avenged Sevenfold (in this case, Nightmare) so what did I do? Tweak my stuff until it sounded an approximation.
Learn the tools, know what certain plug-ins do to the sound (as some are modeled after vintage gear) and figure out stereo enhancers. Stereo enhancement isn't always necessary, but I find a bit is always nice with the way I mix, if the stereo field is already pretty wide, then no need etc etc.
I know how i like things to sound, pretty warm and pretty dynamic. But some people like squashed 0 dyanmic mastering. Also, you can forget about achieving the perceived loudness RMS of modern pop recordings, you'd have to have a perfectly treated room to get that. Just get as close as you can an hope for the best. <3