good point Harry,We always setup the nite before in an empty room of course.In a small venue,the bodies have a big effect on the sound.So sometimes, as Mark B said ,a bit of "fiddling" goes on to acheive a better all round sound, for all in the room.
Regarding stylii,change them on a regular basis(hours used).
Don't forget tho',not all records are in tip top condition to start with,a better stylus will pick up everything. .
DJ'S "FIDDLE" TOO!!! .