I don't wear a lot of makeup and don't know what I want...
Thats fine. That is why you called a Professional, Right?
Firstly I always like to suggest you have images of makeup you like. This isn't to copy, it is very unlikely that you show me a picture of Jennifer Hawkins or Kim Kardashian and I will make you look exactly like that.
The images are a starting point, using these images we can work out what it is you like, A colour, A shape or the whole 'Look". I will ask a tonne of questions about The style of event, The colour of your outfit, Your makeup wearing history or lack there of, Features you like and dont like about yourself... etc. With all of this information I can give you my opinion on what would work best for you for. And of course that is what a trial is for!!