I usually just plug in and go. My amp is always set at my optimal beginning point eq wise, and I make adjustments as I go. For the most part, unless your doing a really small gig, the Amp sound you get on stage is just for your satisfaction. THe more FOH support you have the less your amp matters out front. In my youth, I had big LOUD amps, and was almost never in the mix, soundmen hated me. Now that IM older, I have learned restraint and how to control my EQ. Cant tell you what to do, as its your sound not mine. But thats what I do, just go up with a basic setup and adjust from there. You can always have someone in the audience who knows what they are doing to help guide you, or you can make friends with the sound crew and have them help you.
One thing we ALL have to remember, we play live to ENTERTAIN PEOPLE. Not to have an orgasm on stage at how loud our amps are and how killer they sound. There is a happy medium in there where you can still spooge in your pants a little and have everyone else be happy too. Try to find it, compromise is good.