[Always *]

I agree with Brittany; it's pretty nerve wracking meeting the parents the first time.
The best thing to do is to dress on the nicer side, whatever that means for you, and be polite. Also, be yourself but if you tend to swear try to keep it to a minimum (people like me can struggle in that area so I understand). But don't worry, if you make a nervous blunder, they're not going to hate you. Even as your boyfriends parents, they're still humans and generally humans aren't predisposed to disliking someone for no reason. If the worst they think afterwards is that you're weird, then that's ok. Just breath easy and it'll be over before you know it.