my 2 cents
1. dont master audio using headphones ( i am not saying you are) it distorts the entrie sound. always use good speakers
I actually disagree with this, but only on one condition. That condition being you have some headphones better than your typical phones you can buy at Best Buy.
I have had Sennheiser HD570 headphones for the last 2-3 years and listened to every type of music through them with probably a few thousand hours. I know what music should sound like coming out of these phones, and I do master with them, and things come out great.
The rule I am trying to set is, know your equipment. Listen to everything you can through your speaker or headphone setup you want to do mastering on. There is a line to be drawn on equipment quality to do it with, but a decent pair of headphones costs a heck of a lot less than a decent pair of speakers.