If you want to keep your relationship strong, always be moving into new territory. Test the boundaries and don't be afraid to experiment.
COMMUNICATION: Walk around and have conversations with each other, not just flirting sessions. Get to know each others needs and peeves. If something bothers you, LET IT OUT.
SPONTANEITY: Be a little bit unpredictable. Grab her by the hand and run together to some secluded corner just to give her a kiss. Do something a little crazy.
RESPECT: I'm not so much into the idea of DOMINANCE because it tends to make relationships last 6 months max. Respect is a big deal that encourages a long-term relationship. Make sure that she respects you and doesn't take advantage of the fact that you care for her. Point it out whenever she puts you in a trap ("Do I look fat in this?" "What do you think of that girl over there?"). However you have to give her the same respect.
When you do these right, you fulfill the three basic needs of a strong relationship: Loyalty, intimacy, and passion. Always keep a good balance of these three, and you will be fine.