hmm well when I was in highschool, girls parents never came out so formally with something like "what are your intentions with my daughter?".  I mean the best thing you can do is present yourself to them in a very polite and respectful way.
Before going to their house, make sure you cover the basics.  Shower, shave, apply deodorant etc.  Make sure you wear something decent.  Probably a button-down or polo shirt with some nice jeans or khakis.  I mean you don't have to get all dressed up, but don't go wearing your Dickies and Independent Truck Company t-shirt.
When you go to meet them, you must be very proactive in the process.  Parents hate when their daughter brings a guy home and they are drilling him with questions.  Show interest.  Like as soon as they open up the door introduce yourself.  Greet her father with a firm hand shake.  Not too hard not too soft.  Probably going to do the same thing with her mother, because idk you normally don't hug her or anything the first time you meet.
Anything they ask you, make sure to answer with detail.  They are trying to determine what you are like and if you're appropriate for their daughter.  You should be doing 65-70% of the talking.  And while you are talking, look at their face.  Talk to their eyes.  Liars can't talk to someones eyes.  Also make sure to try to look cool and comfortable.  Don't keep your hands in your pockets all the time either.  Convince them you feel comfortable in their house.
Be observant.  If you ever get hard pressed for something to talk about, make a point about something in the house.  I dated a girl for a while who's father was a big time hunter.  So I saw his mounted trophies and asked him about them.  And he loved the compliments and told me all about his trips to canada and what not.
So for all of you guys, theres a little something on how to deal with parents.  Comes from a few years of experience.  But rememeber, that basically covers your sterotypical parents.  All families are different.  So just have a feel for what you are doing.
hope that wasn't too long