Kissing somebody you love feels good, but I'm glad you're thinking this through. Don't do anything that either one of you will feel ashamed of. Learn to be kind, appreciative, complimentary.
Don't do anything that could cause you to lose your self-control. In fact, they might not have seen their spouse until the wedding day. I've been with a guy for almost a year now, and I don't know how far is too far. The only good answer I know is, "To express our love.