Embrace the scene accordingly.
A crucial part of making her parents like you is not offending them. While this seems obvious, there are many unintentional ways you can signal disrespect, particularly when her parents don't share the same beliefs as you.
The easiest way to avoid an awkward scenario where you do something offensive (aside from asking her about what is acceptable beforehand) is to observe the scene, and act accordingly. If her family says grace before dinner, politely bow your head. If they have a drink before dinner, toast it up. If they eat while sitting on the floor, or with their hands, you do the same. If they're serving food you haven't tried (or even heard of), eat it willingly and enjoy it (or at least look like you are).
Bridging cultural differences, while difficult, is not impossible. It just means being open-minded, aware, and willing to embracing her family's traditions, even if they depart from your own.