Most Helpful Guy
Dads are easy. Don't worry about his dad, he'll probably like you simply because his son does. Especially if you're good for each other.
Moms are harder. Its her you have to win over. Having halfway decent manners, being respectful and tossing a couple compliments her way is a good start.
Oh, check with him about how you should dress. You can under or over do it, ask him what would be appropriate. Mention his mom's opinion.0
Most Helpful Girl
Be polite, smile and don't be afraid to voice your opinions. There is no need to agree with anything they say.0