To make your relationship last.
It’s not a guessing game. Tell each other what you’re thinking, and what you’re feeling. If something the other person does bothers you, tell them. The longer you wait to handle a situation, the more pressing it’ll become on your relationship.
Never let phone calls or texts interrupt moments together. The phone is there for your convenience, not the callers. If you 

truly love the person, you should be more than willing to give them your full attention.

Be honest. Don’t lie, don’t cheat. And if you screw up, admit it. Chances are, the other person will find out eventually and it will not be pretty. Everyone makes mistakes, so be honest and forgiving with your boyfriend/girlfriend.
Discuss important issues early on. It’s never too soon to talk about the future (children, money, etc.). Know what he or she wants out of the relationship. These are important things to know - much more important than what their favorite color is, or what genre of music they listen to.

To men: Don’t you ever dare to forget her birthday and anniversaries.

To women: Never make him jealous
Bring back the old days. The days of flirting and fun. Just because you have them wrapped around your finger does not mean you should stop doing the things it took to get him or her.
Always say goodnight. Don’t let a day go by where you fail to. I don’t care if you’re mad or angry at him or her, it shows that you care and that you can accept and get past your differences. It means: I still love you no matter what happens and that nothing can change what I feel for you. I love you despite our differences. This is crucial, so don’t forget it.
Remember the little things. Maybe it’s something they say. Remember these things, and use them to your advantage. Randomly bring them up, and surprise them. They’ll love you for putting so much effort into listening to them and making them smile.