Please note that I do not work with under 18 models - on any type of project. This is no reflection on the quality of junior models here - many of whom are excellent - it is just a practical decision to simplify things for me.
Chaperones - I have worked with chaperones in the past and some have been a pleasure to deal with - others have not or their involvement has complicated organising the shoots. In the interests of keeping life simple I do not do shoots involving chaperones any longer. I have over 70 references here and anyone planning to work with me is welcome to ask any of the people on the list for an honest view.
No shows/last minute cancellations. Though I do photography purely for fun that doesn't mean I don't don't take it seriously or put effort into preparing for shoots - so no shows or last minute cancellations are a major hassle and take a lot of the enjoyment out of it for me. I now have a "one strike and you're out" policy. I do not reschedule shoots with people who no show on me or cancel at the last minute with inadequate reasons.