"Blend towards the ticket buyers, not each other."
I have seen countless chamber ensembles fail to grasp the vital principal behind the above quote. The audience experience is everything.
Don't sit in the easiest possible configuration for your group to interact with each other. Sit in the configuration which makes it easiest for the audience to feel like they are interacting with you.
Don't just make sure something is balanced on stage. Make sure it is balanced in the hall.
Don't lift your stand up higher than it needs to be. Put your stand at a level where the audience feels like they are a part of the experience and not just allowed to peer over your shoulder.
Don't just check for dynamic contrast on stage. Make sure that contrast is reaching the last row of paid seats.
Don't match articulations on your side of the bell. Be sure they are matching at the back of the hall.
This list could go on and on...
I couldn't believe how much left edge I had to put on notes when I first joined Boston Brass. Like, I was dumbfounded. What my colleagues were asking me to do sounded stupid on my side of the bell.
But guess what? Those comments were coming from a rehearsal technique that we frequently used. One player would go out into the hall and listen from out there (ie the only place where it matters what it sounds like!) They would then ask for adjustments until it sounded right out there.
They would ask for so much attack that I thought it sounded stupid. But I trusted them so I did it.
Then I would listen to a recording of the performance from later that evening and I'll be damned they were always right. I had to very gradually adjust what I thought it "should" sound like on my side of the bell.
I have yet to find anyone who will pay me to in an orchestra, band, quintet or as a soloist based on me sounding good on my side of the bell. No one cares.
Literally your only job is making sure it sounds (and looks) good in the audience.