I got a 25 watt peavey, if I'm playing clean I put the volume up to 2-4, if I'm playing with gain I put the volume at 1-2 with as much distortion as I want, usually 5 or 10. All the guitar knobs up all the way, neck pickup. I use the headphones coz it's easier to pickup mistakes but can you hear the clicking of the metronome over the sound of the guitar right in your ears? There's not really a visual cue on the analogue coz it's too hard to pinpoint when it's exaclty centre isn't it
I usually use two sets of headphones and just hang one over each year, one coming from metronome and one from my amp.