One of the few relationship milestones that I know I have in the bag is meeting the parents. Parents have always been my specialty, for some reason. It's so seldom that I can actually give advice on something rather than just speculating so I put together a list of parent-friendly pointers. A few 'Do's and 'Don't's:
Do Ask your SO a ton of questions ahead of time. There's no better way to figure out where your boundaries lie. Is his mother crazy about raising exotic ferns or is she allergic to everything containing chlorophyll? What's Dad's favorite sports team? Or is Dad more interested in model airplanes (in which case...honey, I haven't seen any actual model airplanes anywhere in your parents house. I think your dad is just huffing glue in the garage.)
Don't overshare. These people are parents, not your girl friends and they probably aren't going to be won over by that story about how you had one too many dirty martinis last weekend, snapped a heel off on a crack in the sidewalk and had to walk home with one shoe on. (I love that story, though. You can always tell me again.)
Do bring a little something. Two of the most important things in my life are drinking and baking and that's very lucky, because everyone loves wine and cookies. Together, obviously. If you aren't skilled at channeling Betty Crocker, it can be tempting to want to just grab a store-bought pie but I'd advise against it. Play to your strengths, whatever they may be.
Don't step on anyone's toes. Ask if there's something you can do to help out, but only once or twice. If Mom consistently says no then, well, she means no (and, possibly, "You're getting in the way.") Sit down and enjoy yourself.
Do your best to charm their pants off. Tell them how great their son is and how lucky you are to have found him. Point out evidence of their excellent parenting. They will glow and coo and be deliriously happy. This is where you can overdo it a little, within reason.
Don't compare them to your own family!! I can't put enough exclamation points after that one. Every family is quirky, dysfunctional, damaged, and awesome in its own way. Take comfort in the ways that his is more supportive or social, or how yours never argues on holidays. The words, "Well, we don't do it that way," should never cross your lips. You're on vacation in a foreign family. Don't ever be a rude American.