I have two tricks that never fail, both have probably been mentioned:
1) Never dial "blind". Have some kind of reference to compare against. What I use is one of my drum programs--I'll just let it play a groove and start dialing along to it. All I'm looking for is roughly the same sonic fidelity/clarity. From there, dialing in the amp gets significantly easier and the decisions I make become more trustworthy and keep me from coming back days later only to realize my tone was too dark or doesn't have the kind of texture I want the tone to have. I think we've all been there many times, especially with modelers: you love your tone one day, then the next, you call up that patch and go "wtf was I thinking?!" and end up in this endless cycle of tweaking. Having a reference track to which you are dialing takes a LOT of unnecessary guesswork out. Just make sure there's no mastering chain on the bus, otherwise you're gonna be too bright when it comes time to put all that stuff on.
2) Dial in your patches pretty loud, even in headphones (which I recommend because you want to hear intimate details like texture...not just of the amp, but your effects too). The obvious reason is the Fletcher-Munson curve, which is accentuated at low volumes, and you're mainly hearing the high and lows, so you end up compensating in the wrong direction. Setting this stuff up loud helps you hear how much low and highs you TRULY need, especially in a live or recording context. One warning though: don't be at it for an hour, obviously you'll damage your hearing. Maybe 10 minutes tops and then walk away and give your ears a rest for a couple hours if you haven't finished. Honestly, that doesn't happen often though because once you tweak your modeler using these 2 steps, it goes by pretty quick. You simply are making better decisions because you can hear everything in intimate detail.
These two tricks have never let me down.