First makeup trial today...what questions to ask?

Go in there with specific ideas. What colors work for you. I'd go in with your every day makeup on or even an attempt at your evening makeup so they can see what you like.
Also - they probably won't want to show you what is going on until the end - I was shocked at how bad my first trial was and how she apparently didn't hear a word I said.
It might be better to let them know how it's going before they finish.
Make it clear what you want. I thought I was specific (asked for pale lips and I got dark brown liner with very dark lipstick about 1/4 inch outside my lip line)
I am now going to do my makeup myself because I honestly think a lot of these makeup people take a 2 hour class, buy the makeup and call themselves makeup artists.

I know it sounds strange - but I really would ask about training and experience.

If they do airbrushing - consider only if you have PERFECT skin and never use any concealer. It is so sheer, highlights every fine line and cannot be used with concealer. In my opinion - it's horrible but I don't have perfect skin!

jmo- give her a few indications as to the type of makup you usually wear or what type of skin you have but i say let her do her job. when i went for my trial i let her play around and chose the colors for me (i'm not a big makeup person) and she said if i don't like it we can revise some of the colors.

but i would ask if you can purchase the lipstick for the day of.