We got my daughters first haircut at about 17 months and at Belle Capella's. It was a tiny expensive, but I got to take pictures and they cut a few curls and tied them with a bow, and gave me an owner and stylist signed "first Hair Cut" certificate. I really had NO ideas what her hair should look like, so it was nice to be able to trust a good stylist to give her a nice haistyle.
Also, just a trick I learned to keeping your child still during the cut. Bring a few tootsie rolls for her and give her one (or even 1/2) as soon as the haircut starts. She'll keep still and the reward of the tootsie roll will be a nice little reward for being a big girl and getting her hair cut like a champ! My daughter LOVES getting her haircut and I think it was because the first haircut was really a possitive experience. Some kids HATE it and scream the entire time. Make this first time a good experience for long term.