Are you on the same page about money, kids, housework and sex? These are some of the things I see couples arguing over. Talking about them before you move in together or marry could save a lot of grief later. Don't just assume you can work it out, because some differences (like whether to have children, and what you will do if you can't) are especially challenging areas in which to create a compromise.
I caution couples that it's not only what you find out through the conversation, it's your style of communicating that matters. Being able to discuss serious topics with respect and having the feeling that both people listened to each other and worked to create agreements -- that's an important part of being ready to making a bigger commitment.
If you need help leaning to communicate well, or if you need help with learning to work things out together, let's talk. I have helped many couples learn to talk in a way that works better, and to work together to create solutions instead of scoring points.
Here is an article from Canadian Living magazine that was just published, where I was interviewed on six conversations to have before you marry.