Basically there aren't any hard and fast rules on EQ, because it will always depend on the frequency content of your tracks. However, there are a few things that I find myself doing a lot:

• -Remove any bass below 20hz: Usually I remove anything below 50-60hz because I don't think it's really relevant. However, the lower limit of human hearing is 20hz. So, you're always safe removing that. If you actually have any content down there, it will just be messing up your levels.
• -Interlock bass drums and bass It's important to check your bass and kicks to make sure they're not interfering in a weird way. Usually this means cutting some frequencies in the 60-120 range on one, and boosting them in the other. Use your ears for this.
• -If something is getting buried in the mix, try cutting the bass out a bit and boosting the mid-mids up to the high-mids and see if you can get it to stand out a little more.
• -To boost presence a bit: do a wide cut in the entire midrange and then boost volume. You only want to pull it down 1-3db, though.
• I've found that the Fruity Parametric EQ 2 (from Image-Line) is really, really useful for tweaking EQ in the mix phase because it has a spectrogram displayed underneath the EQ controls, which makes it easy as pie to find trouble spots and fix them. The danger is that you won't listen as closely to your mix, and will be fooled into thinking you can do it all visually, but it does save time overall. Hope this helps!