Based on my experience with my two cesareans, my VBAC, my experience in supporting moms in giving birth, and my VBAC preparation classes, the following summarizes VBAC success in a nutshell:

"The most important factor in determining whether you have a VBAC is your choice of doctor or midwife and the place where you give birth.  It's not why you had a cesarean, or even how many you had.  It's not having a birth plan, or how many books you read.  And it's certainly not whether you attended a VBAC class or how many miles you walked during your pregnancy.  All of these are significant, but they're not number one."  From The VBAC Companion by Diana Korte (page 89)

Read that again.  Let it sink in.  You can do as much preparing for as long as you want, but if your providers do not believe in your ability to VBAC, your chances of success significantly decrease. SIGNIFICANTLY.

Here are some important questions to ask of your provider to help you understand how supportive they will be.  I would present these questions, modified as appropriate, to ANYONE you are paying to help you VBAC - a doctor, nurse-midwife, midwife and even a doula or chiropractor.

1. How many VBACs have you attended?
2. Of those women in your practice who wanted VBACs, how many were successful?
3. What do you think my chances are of VBAC success, given my childbirth history?
4. (For a doctor or CNM) What is your cesarean rate?
5. (For a home birth midwife) What is your transfer rate to the hospital?
6. How do you usually manage a post date pregnancy or a suspected CPD (cephalo-pelvic disproportion)?
7. What is a reasonable length of time for a VBAC labor if I'm healthy and my baby appears to be healthy?