A strange recommendation, to be sure, but I did this a few years ago - the three-day seminar on producing for the commercial theatre for CTI. I'm not interested in producing for the commercial theatre. But for a playwright, this was a very interesting and valuable experience, and it does give you a great appreciation for what someone goes through if they want to produce theatre anymore.
It also lets you - as a playwright - know what would be appropriate for a producer to ask for in a negotiation. And what would be completely off the chain.