pretty simple question.

i have an amp with 2 channels that each has a volume, and also a overall master volume.

which volume should be maxxed out? the master volume so i can control each channel . or should each channel be maxxed out and i use the master volume to control all?

and why
i wouldn't dime either of them, you adjust them to your liking. What amp is it BTW?
I keep my cleans' volume at 10 and my distortion's at like 6 to balance out the volume. Also, I find that if I lower the distortion's volume, I get less bass and mids.
Jackson RR5 ivory w/ EMG 81/85
Jackson DX6 w/ SD Distortion & Dimarzio Super Distortion
Fender Starcaster Sunburst
Mesa/Boogie DC-3
Johnson JT50 Mirage
Ibanez TS-9
Morley Bad Horsie 2
Boss CE-5

ISP Decimator
Boss DD-6
Korg Pitchblack
well if you got two channels... those other volume knobs are for that channel only... so you can turn that volume down along with the gain up... if you want a good chugg chug chug... then the master volume controls the main part.. so that channel volume can be half way.. and if you turn the master up., it will still get louder.. hope that makes sense
i usually thought it was best to set each channel volume to where they sound good together with the correct gain levels, and then use the master volume to control the overall loudness of the amp. that is usually not going to require either volume knob to be maxed, but you can do that if you would like.