I know this has been said many times, but get Bob Katz's book
Mastering Audio: The Art and the Science and read Chapter 8 (Equalization Techniques) and Chapter 3 (Earientation Session.) A wealth of info on thinking about how to use eq and qualitative effects.
In Chapter 3, there's a great chart that translates subjective terms on sound to frequencies that will help you decipher what you're hearing to make eq choices (and what cutting and boosting will do.) I looked to see if that was a chart taken from somewhere else so I could link to it, but it appears to be a Bob special

so you'll have to buy the book to see how valuable it could be for you.