The importance of an interview
Most doulas will meet you for a free, no-obligation interview. The purpose of the interview is to find a doula who is a good fit for you and your partner. No doula is going to be perfect for every couple. Since this person is going to support you through one of the hardest and best days of your life it's important to chose someone you feel comfortable with.
What's done at an interview?
An interview can take place in your home, over the phone, or more commonly, in a public place such as restaurant or coffee shop. The doula can tell you a little about her services, but the most important part is answering your and your partner's questions. A good idea is to have your questions written down so you don't forget. Be sure she's willing to do what you want her to do in labor. Every doula has her own areas of expertise.
What happens afterwards?
If you love the doula you just met you may sign a contract at that time. Most of the time she may require a deposit or the entire payment depending on were you are in your pregnancy. Feel free to say goodbye and interview other doulas before you make your decision, however. Try not to take too long, though, because doulas often only take a certain number of clients, and her schedule may have filled up since your interview.
What it's not
Keep in mind that an interview is only a preliminary meeting. It's not a childbirth education class or a prenatal appointment. It usually only lasts 30-45 minutes. It's also not an obligation to hire her as your doula. If it doesn't feel right to either party the doula can give you recommendations for other doulas in the area.