I'm not an expert about relationship, but I know perfectly which behaviors I would never tolerate, or some aspects to create a better relationship.
The first advice to get a healthy relationship is supporting them, making them laugh, playing with them, or even having your own private life apart from your partner. Sometimes we feel anxious to know everything about our partner's life, but you should give them space to have privacy.
Another advise, a pretty basic one, is never playing around with other people. This will break the confidence and it will never be as before. If you do that, your partner will think that you laughed at them, and they might think you are naughty. Even if it wasn't it your intention.
The last advice is do not look for romance, it will appear when it has to. If you are desperate for love, you will accept everything gladly, and it is not a healthy way to start a relationship.