In most practicality, the guitarist, and/or drummer (!), will set all their volumes at max and just stay there. (sigh) But you can at least start off as "the voice of reasonable volume" and give them a chance to turn down (it could happen) or, if "the party is truly hardy" you can judiciously increase to match, as you see fit.
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This is a great point. As a guitarist, it took me a while to figure out not to play with my volume on 10 all the time. Once I started rolling down my volume, even in high gain situations, I had more tonal flexibility and could adapt when I needed to re-mix myself on the fly.
As a bassist, I take those lessons I learned on guitar and have applied them. I run my volume and tone around 6. Yes, it's more flexible. But I also know I can adapt as the band's volume inevitably rises.

