Studies have shown the Four most important topics to discuss before marriage are #1-Money, #2- In-Laws, #3-Children, #4 God/religion
I will definitely add Sex as a fifth. I call them the Five Pillars to a successful marriage.
I believe it is vital that you discuss sex before marriage. Especially if you plan on not having it before you get married. Both should discuss their expectations for sex, what they are willing to learn about with each other, what they are not willing to do.
There is a great book called The Act of Marriage by Tim LeHaye that I highly recommend to soon to be married couples as well as anyone else. He is a pastor and comes from a spiritual place, yet is so detailed and straight forward in his explanations when Shannon and I read it while engaged, we could not read it together. We would have to read separately then discuss after each chapter what we thought and had learned.
In my practice I have become more and more convinced, if more people had open and honest discussions about sex before and after the wedding date, there would be less contempt over other matters and therefore less divorces.