sodbuster said:
just watch the family dynamic,does mom respect dad or is he the worthless wage slave? Do they know how to act or are they arguing all the time.Most times,just like with women,you can't ASK. you have to OBSERVE. I mean, they'll tell you what they do etc.,but some of the important stuff won't show up until you WATCH.
A BIG red flag is if she has NO female friends. Just like a guy with no male friends.
Sodbuster is right about observing but that's only half of the solution. You have to know that every family is different and not every family is like you own. Not even close. At the very least, learn to set limits of what you say and do in front of them and definitely mind your manners.
About questions:
Unless the dad drives a ****ty ass car, I usually make some sort of comment about the car to him. Sometimes I'll even lie and say my parents used to have that car, just to build rapport. If you don't want to talk about cars, ask him about anything, his job, where he came from, anything.
With the mom, it's a little harder but usually the mom does most of the talking anyways. Compliment her on her kitchen, or on her rug or anything.
All of this isn't very important at the start. At first, the parents are going to be qualifying you like crazy. So be prepared to answer the basic stuff- school, career, family, etc. Talk slowly and confidently.
I'm not sure how well this works, I've only tried it a few times, but try to value yourself a little lower than her father. Meaning, if her dad's an extremely confident guy, act very confident yourself. Just don't stare him down every single time, let him have dominance. Same idea if her dad's a chump, let him dominate you and he'll have empathy for you -"he's a really nice guy."
The general lesson is like sodbuster said to OBSERVE, but not only to observe but to adapt. More importantly, you should learn. You WILL make mistakes and that's fine, as long as you learn from them.