Rant/Surcharge?

 Bummer! I've never had that happen, so I'm afraid I don't have any suggestions on a policy for how to handle it, but I can give you some tips on how to avoid it. I have a $50 deposit for hourly jobs, but no cancelation fee for individual appointments. I take them in my house so no-shows aren't much of an issue for me.

Some one who is trying out a tattoo is always a red flag for me. I always go out of my way to explain the process and result and make sure they're in. 

If a "tattoo" person is not sure about the whole henna thing once they understand it, I suggest temptu. No, it doesn't last as long, but it looks the way they expect it to.

For any appointment, I ask if they've had henna before. I also ask if there is a particular event they want to show off the work. This gives me the opportunity to probe into what they expect, and help them schedule in a way that makes the most sense.

 That's rude.

I would say, charge people half or something upfront.  Or 10$ "travel fee" or anything, just so that they won't take off, because they've already put something into it.

Did I mention, that's rude?

Like Jen, I give them a quick run-down of the process and what to expect regarding color and its life cycle.  I also let them know what their responsibilities are if they want the best results and a price is either settled on or an approximation given, including any travel charges (based on mileage or commute time).  This is all done before an appointment is made.  This kind of discourse  (along with a deposit, if applicable) weeds out the flakes and leaves less chance for misunderstanding and wasted time. 

I get a lot of business from people who want to "test drive" a tattoo idea, and about half of them prefer it done in black Temptu, which is a great product and very useful to have in your repetoire. 

 When I suggested a "travel fee", I meant it would be like a deposit, but labelled as a travel fee.  People might be put out by a deposit, but not by a travel fee.  You could apply this to the final price of the appointment, just like a deposit.

Or, you could just mention, "Due to people cancelling without notice, I now charge an xx$ deposit, which will be applied to your final bill."

I don't think it's unreasonable, I mean, think about anything, a concert, a movie, if you buy a ticket, and decide not to go, you don't expect to get a refund.  At the best, you would get to exchange your tickets for something else if you called before the show.