When you’re meeting your partner’s parents for the first time, bring food! Bake cookies or make your famous potato salad.
Be pleasant, be kind, be yourself, and expect the best. Carefully consider your degree of disclosure until you’ve had a chance to get to know them a bit.
Other than that, you have no control over whether your partner’s parents take to you. If you’ve done your best, that’s all you can do. Let the rest of it play out as it will.
A couple of final caveats. Refuse to compete with your partner’s parents for your partner’s time. If he’s not making you a priority, he’s not the right person for you. And if he’s taking his parent’s side against you, oh my word, don’t walk away, RUN.