For me, this is going to sound strange, but one specific thing that I can point to is when we were dating, discussing becoming engaged, and he brought up children. He said that he absolutely wanted to either have his kids homeschooled or go to private school (both of us had gone to public school, although only high school for him as he'd been homeschooled until then). He also said that he really wanted to foster or adopt some children. The thought that he had really spent some time thinking about his future children and what he wanted for them spoke volumes to me about his plans for the future, what was important to him in life (he hadn't figured out what career he wanted yet), etc. I had never really thought about how I wanted to educate my kids, but after spending my public school education having daydreams about being homeschooled or private schooled or something, ANYTHING other than my public school, I was very amenable to it.
Also, we had been dating for three weeks when he started asking me how soon I thought was too soon to get married. This, after he had waffled for several weeks over whether we should date at all (after we had mutual friends reintroduce us and we hit it off). He told me that he'd decided that he had decided not long before we started dating that he was ready to get married, should opportunity arise. The fact that he looked upon post-college dating (or, well, end-of-college really) not as something fun to do on the weekends, but as a specific path to determine whether or not you and a person would make good mates, and if you decided that, then why wait too long for the wedding, made so much sense to me.