I only accept bookings via the phone and I only accept same day bookings minimum 1 hour notice, if i get an email I give them my telephone number and ask them to call me only if they want feedback or to make sure they have a confirmed booking will I use the AW booking system.
With newbies when they call in in the morning for an afternoon appt I will ask them to still confirm that they are still coming by phoning me when they are either on their way or an hour before their appointment time, without this conformation I will know they're not coming.
I find when a man gets gets my details over the phone and then says "I will try to call you later" or "I will probably call you later" he wont.
Another tip is when I give them my post code a minute later I will ask them to repeat it back to me and if they cant they havent taken it down so are going to be a timewaster.