Here's the list:
1. Travel together. Whether it's a long trip, short trip, or even a day trip, it's important to travel with your partner, before committing to each other for a lifetime.
2. Questions, questions, questions. Make sure that ask each other a lot of questions. Make sure that you're both on the same page and ultimately, you both want the same things in your future. This is actually something that should happen during early dating (see: "The 3 Date Rule"), but make sure that it happens regardless.
3. Make sure that you want to get married for all of the right reasons. A relationship should be based on a solid foundation built upon honesty, trust, good communication, shared interests, and you should have a connection on as many levels as possible. As well, it's important to make sure that you have the type of chemistry and attraction with each other that will grow and change, but that will last a lifetime.
4. Make sure that you've figured out how to resolve conflict together in a peaceful manner. Look at how you make up after arguing, and make sure that you've learned never to go to bed angry, and to always kiss each other goodnight before going to sleep.
5. It's important that you make each other into better people. You should support each other in the things that you're passionate about and always have each other's backs.
6. Make sure that you've established that you're each other's best friends. Having other friends separate and together is great, but being each other's number one best friend can make a marriage last forever. Best friends trust each other and share everything together, with full disclosure and an open book mentality. You should be able to confide in your partner and trust that they won't judge you for sharing and opening up to them.
7. You should have a discussion about the roles that you'll be leading in your household (to some extent) once you get married. You should at least have somewhat of an idea on this. Whether one or both of you is going to be working outside of the home, in the home, and whether one of you will be staying home, being a homemaker, and whether or not you both want children, etc.
8. Depending upon how intimate you decide that you're comfortable being with one another before marriage, it's important to be on the same page in that regard. Having said that, either way, you should make sure that your passion is intense and exciting enough that it will help when times get rough. Amazing passion can keep the fire and chemistry alive throughout your marriage, and especially, after getting into an argument. This is where the term "make up sex" comes into play.
9. If you're both planning on having children together one day, it's important to talk about what parenting style that you plan to raise your kids with. For those that don't know, when you have different views on how to raise your children, it can cause a lot of problems in your marriage and in raising your kids. If one of you wants to raise your kids in a very permissive parenting style which allows the kids to do whatever they want basically, an authoritative parent might not sit well with that idea. An authoritative parent believes in having discipline, boundaries, and rules, with a lot of affection to the kids. It's important to be on the same page as far as parenting goes. As well, you should talk about how many kids you're both hoping to have (with G-d's Blessing, of course).
10. If you're considering getting married, it's important to know each other's dreams, and what your hopes and aspirations are for the future. It's important to believe in each other and help each other achieve those dreams and goals.