Broken expectations is the chief cause for many divorces IMHO. When many of us are bitten with the love bug, our rational thinking flies out the window. Heck, being irrational will give us some of the greatest joys in life - when we can say, "I did it, I didn't give a damn about what anybody thought, I was wild and I did it!!" But when reality hits us and we wake up in a world that we didn't imagine for ourselves, the crappy part about being irrational hits us like a Mack truck.
I encourage some pre-marital counceling from a professional or a decent minister (WHO HAS BEEN MARRIED for a while). A few books about relationships can be helpful too (your pre-marital councelor can recommend some). If you get the feeling that your councelor is a moron, find another one because they probrably are. Most of us know someone that can recommend someone who's not an idiot. Trust me, there are a billion idiots out there giving people advice, but there are also a great deal of level-headed folks that know a thing or two about relationships.
This is what you need to learn in pre-marital counceling:
1) How to make a budget and more about home finance
2) How men and women relate to eachother sexually. Ok, most of us figure out what sex is all about before we get married, but knowing some stuff about sexual needs from a knowledable person can really solve some problems in a marriage. Ever thought you knew how to fix a car and found out that you need a mechanic? hmmmm
Sex is a wide, wild and crazy universe. Find a good map.
3) Problem solving - you need in-depth training on conflict resolution. There are conflicts in marriage (DUH!!), so having a plan and training really helps. Divorce = unresolved conflict
4) Life planning. Find out your life goals BEFORE you get married, or at least a life sketch. Marrying a lazy bum may not be the best thing for an over-acheiver.
EDIT: Always ask your counselor if they had a divorce. You don't want to take advice from someone who failed in this regard, particularly if it is your goal not to be divorced. It's like the old proverb, "Never trust a skinny cook." Divorced folks know a thing or two about broken marriages and unmarried folks can learn a great deal from them, but all they have is theories for keeping one together. If your conselor downplays or does not address these issues, find another person to talk to because you are not getting good advice that is worth your time, and preparing for marriage is worth it.