This can be a personal question, and each doula may or may not have a similar answer. I'll start with what we were interested in for our birth.
1. Somebody who would be accessible to us - so flexibility was very important. We both worked shift work through the pregnancy, so our schedules sometimes looked quite difficult to crack. We were able to find a doula who was able to see us at our convenience.
2. Open mindedness - this was important for us. We had a difficult pregnancy and jumped through numerous health care hoops to find continuity in prenatal care. We were stressed that our birth choice had gone from a home birth to a hospital birth. Our doula was open to our home birth option but presented us with all options on the spectrum.
3. Professionalism - I work in health care, so I know what to expect from nursing care and physician care. I would expect the same from my doula.
4. Good references - We were lucky in that we had friends who had accessed our doula as a midwife and had given us her name. She came well prepared with a portfolio of her births, letters of recommendation, certificates, and a good following in our city. I would return a good reference to her to this day!
5. Cost - I had all confidence that if my family needed doula care, we would be able to receive it regardless of our income.
We all want different things for our birth. The important thing is that your doula is supportive of what YOU want as a birthing family. Her role is to be there and provide safe and competent care. The best advice my doula gave me was to interview a few people.
I was concerned with my birth about the timing, as my doula was busy a few days before my due date. We had set up a back up, just in case, but we ended up being okay. My philosophy will be to anticipate the need for a back up and ensure that the client will be familiar with who she is.
Being that birth can happen any place or time and is relatively unpredictable, your doula will typically need some amount of time to reach the destination. Typically your doula will need to be kept updated about what is happening in the pregnancy in the late stages. Then it will be as simple (or complicated) as meeting the parents at the birthing place of choice. Factor in brushing of teeth, changing, driving, as well as making arrangements for other children!
You may also find this article helpful: What Can a Doula Do For Me?
Read more of Rhonda's work on her blog: http://birthingutopia.blogspot.com