As someone who does all the booking for my club I have a few ideas on what I look for in a demonstrator.
Most have been covered in this thread and I agree with most of them, where they apply to a single night. I do however have to think of the club and that primarily means the members.
I have to have a program that keeps them coming back, bums on seats really do matter. I have nine bookings to complete for any year, and I have to consider the cost, and we cannot afford the top liners every month. Fortunately I have so far, found that some local turners will come for a modest fee, and these help to cover the cost of the more expensive demonstrators. We do not exclusively rely on turning, I book at least one wood related demo every year, and these go down well. So far we have had a talk on archery, carving birds, a luthier, a chief ranger from a local park and a walking stick maker. Our next session is with the supplier of blanks for the shop we use as a venue, he promises to tell us about seasoning and preparation of blanks and a short turning demo.
When I start to book for the coming year, I have 2016 sorted and started on 2017 already! I look for the well known and consequently expensive turners, and the lesser known ones. I have on several occasions booked blind, and so far they have all been successful in entertaining us.
I try to avoid booking the same turners two years running.
What do I want from a demonstrator? Well to know about them for a start, not just who does a good demo, we are beginning to get a handle on that, but to know who will demonstrate, not all of them will have their contact details in the AWGB web site, and word of mouth helps but only up to a point. If we don't know who you are we can't book you!
I need their contact details, and I collect business cards at shows and talk to any one who may be able to help.
I will contact a demonstrator with a date, usually by email, and I get a quote for the costs and in the month preceding the demo I contact them again to see how we can help them during the evening.
What I need most though is good communication, I have lost count of the enquiries I have made to demonstrators who do not respond to an email.
It helps if they turn up on time and so far they all have, and to let me know if they have a problem, I have had to get some in at short notice in the past.
A lot has been said on whether the audience asks questions of the demonstrator. We get a few and I find for a really good demonstrator the questions get save for the end of the evening when we are all trying to pack up and go home.
Ron