in my opinion (based on pressing new productions, not vintage material), the first pitfall too avoid, if possible, is not paying too much to get the rights on the music you want to manufacture (say hundreds of pounds, not thousands, if that mean anything). then make sure you pay standard prices for master/laque/stampers (i.e. avoid some "big" mastering studios who claims they will enhance a lot the quality of your music y using their machines). afterwards, one advice i would give is to press in large quantity (if possible 1000). you may end up with a large stock but if the music is good and well pressed (and it has to be), then you will sell enough...(if they well distributed, and in time).
best luck with it