Simple, do what you say you will do at a time you agree to do it and use images that accurately portray how you look.. If you can't do something be upfront about it and if you can't meet at a time agreed let the client know an accurate alternative rather than 5 mins turning into half an hour.
Now I appreciate there are a lot of unprofessional clients out there but being able to deal with them is another sign of professionalism..