Communication, and confidence in your own sexuality, are the key. By confidence, not being shy, verbally telling him what do or not to do, knowing how to express what you want when you want. I'd start with oral sex first. Vaginal orgasms are a little different... I tend to cum more from oral sex.

I've been with the same guy more than 10 years now, and we were both pretty sexually shy to start. He was a virgin in his 20s, and I was used to being submissive in past relationships. Long story short, we're now at the point where I'm totally confident in masturbating with a giant dildo right in front of him while maintaining eye contact like we're having a conversation at the dinner table instead. That level of comfortableness isn't always easily achieved, and takes work on both sides. It is really refreshing though to not be hung up on sexual anxieties in a relationship, trust me.