First- Find a photographer that you find online the you like their style and the check out the pricing to see if it is in your budget. Also ask girlfriends if they have referrals that they can recommend.
Second- Once you have a photographer that you have decided upon, check the reviews online. Google, Facebook, Yelp all keep reviews and can indicate whether the photographer and studio are reputable.
Third- Ask questions. Find out whom will be doing the session. Ask if make up is available or if you can bring your own make up artist.
Forth- Inquire about the security of your images, where they will be stored and for how long.
Fifth- Make an appointment with the studio to see the sets, props, furniture, and meet the photographer.
Sixth- Do you click with this person who may see you semi clothed? You should feel completely at ease and you should be able to have that intuition that tells you that.