I always start out the same, no matter what amp or guitar combination I'm using .. first, set your amp up to get the most natural "crunch" or distortion. Usually, that will be just simply turn the Pre-Gain or Pre-Volume all the way up and set the Master-Volume to a comfortable level.
Then, switch on your distortion or overdrive pedal with the level set at about 12:00 to 2:00 and the distortion or drive control at it's minimum .. now, slowly turn up the distortion/drive knob while playing chords til you get the exact right amount of "oooooomph" ..... it will probably be different for every guitar/amp combination you try. It's easier if you can get a friend to slowly adjust the knob while you crunch away on the guitar.