Hi Rita,
Basically the consultation and trial is to find out what type of look she wants, have her pull pics off the internet of what look she's going for. Then you sit her down, do her makeup to what you think she's going for, and at the end you have her tell you what she likes, and what she wants to change. Then you tweak it, show her again, and hopefully that second time you'll have a winning look. Write down all the products and colors that you used.
Usually takes about an hour. If it goes over an hour I charge them more because some people like to abuse your time.
Hope this helps
LC