The venues I play have pretty good PA systems, operated by either our dedicated FOH engineer, or a house engineer. My approach is to dial in my tones in my music room at home, using studio monitors that are FRFR, making the assumption that my sounds will faithfully translate to a larger system. I build and practice my tones at moderate volume, then do a final solo run-through at stage volume to listen for tonal changes at volume.
The band usually does at least one full-show technical rehearsal before big shows, and I have our FOH operator keep detailed notes on what he wants adjusted for all instruments. Most of the time he keeps my guitar channel completely straight with no board EQ, only making adjustments when he hears frequency buildup in the room. The usual culprit is the combination of guitar and keyboards, since we're both covering a lot of the same sonic territory. If the low-mids get oversaturated, the mix sounds tubby and inarticulate. If it's just the room, then he'll make the one-time adjustment at the board. But there are times during the tech rehearsal - usually when we're bringing in new material - when he'll suggest that either the guitar or keys need to make an adjustment for the sake of the entire mix. It's the kind of adjustment you can't predict until you hear the entire band together.
Definitely practice your sound at stage volume. You might try creating three scenes for some presets [darker - neutral - brighter] so you can experiment with the EQ curve during rehearsals based on what you're hearing. If you consistently go for the "brighter" patch, you might need to make that your new baseline.
If you don't have access to a flat-response PA or speaker system for practice, consider getting a really great set of flat-response headphones. There is a whole thread about headphone preferences for AxeFX, and you can dial in very reliable tones using them.
All my patches are stereo, but "mono-friendly". So I can either provide a nice stereo patch with left / right hard panned, or I can just provide a single input on smaller stages. I don't use big crazy ping-pong delays, or wildly separated modulation effects, so this isn't an issue.
Above all, take notes along the way. That's where you will develop a better sense of how your system behaves between your home and the stage. I went from "brand new AxeFX owner" to "on tour with my brand new AxeFX" in less than two weeks. I knew it was going to be a quick immersion, so I had an aggressive game plan for getting familiar with the system.
