EQ is an amplifier for a specific frequency range. you can cut or boost the amplification of the specified Hz. parmetric eq allow for control over HZ, Gain, as well as Q( bandwidth). Shelving EQ has only gain and has a fixed Q and HZ. semi paramentric has a limited Hz and gain with a fixed Q. When experimenting with your cut/boost a good thing to know(remember) every 6dB doubles the signal or cuts it in half.
Separation helps. Use shelving EQ till your confortable with parametric EQ. They are easier to use.
Here is a link to some Hz chart I found off of google. maybe this will also help you.
http://www.makinmusic.net/enter/images/Voice-Instrument%20Frequency%20Chart.jpg
Good luck! I hope I helped you. let me know if I could further assist.