How does a professional typically set the amp for a live audience...As in, do they set it so it sounds the way they want it, when off to the side of the cabinet, or, so it sounds the way they want it where their directly in front of the cabinet. (obviously these two scenarios would be quite a bit different)
Usually so that it sounds good through the PA, using a mic, then adjust the levels through the board so that the mix is good. Without a PA, you have to use what works with the rest of the band.
if theres a pa make it sound good where the mic is going to be(in front of the amp)

if there isnt a PA so where it sounds good a bit father(and also a bit louder)

alway eq the amp to fit in with the band(in my case mids high highs low and bass a little down) you have a bit more leeway with a pa since the sound guy will be adjusting your levels and eq(or thats what he should be doing)