This is such a great question.
I think that the first step towards reaching an orgasm with a partner is being able to have an orgasm by yourself. Masturbate! Take your time, experiment, and decide what is and what is not pleasurable.
Then, bring this knowledge into the relationship. Communication and open dialogue are essential in intimate relationships, and it's important to be able to express your desires to your partner. If something is working, tell them, and if it isn't - or you want to try something completely new - speak your mind. These conversations can be difficult to have, but a caring partner will listen and respond.
Lastly, it can be helpful to try and just appreciate sex without focusing entirely on whether or not you have an orgasm. Being in the moment, and enjoying it for what it is can alleviate stress about the potential destination, which can actually make it easier to occur.
Ari, SHARC member