One thing that frustrated me about pedals that model amps is that I never knew how to approach dialing in a sound. I reckon start with a amp model that is as close to the amp as the player's actual one and work through setting up the rest of the patch around that. Save a few iterations with different eq settings and see which one works best with your guitar(s).
http://www.uberproaudio.com/who-plays-what/199-iron-maiden-dave-murrays-guitar-gear-rig-and-equipment
For Dave Murray, it's a Marshall (JCM) with a Tube Screamer for boost/lead, occasionally with a uni-vibe thrown in and a wah. Sure you can find his amp settings (bass/mids/treble/presence) somewhere...
One thing to experiment with : modelling pedals generally sound better run through a full range speaker (E.g. not a guitar amp). Something like an acoustic amp, keyboard amp, powered speaker - you get the idea. Guitar amps usually have speakers voiced for guitar and the modelling pedals just don't seem to get the tones through that you'd hope for. Run a mp3 through a guitar amp and then a acoustic amp and you should hear the difference I'm talking about.
I run a little ibby acoustic amp for the modelling stuff and it sounds that much better than a guitar amp.