Be on your absolute very best manners around them, don't just say please and thank you also use sir and ma'am. Be respectful and don't say anything you wouldn't in front of a child. I don't know if you'll be pressured about the LDS church, but if so just tell them thank you for the invite, but you're happy with your denomination. I had a good friend whose dad was not only a Johovah witness, he was also a state trooper. He was strict is putting it mildly, but he really liked me...thought I had very good manners.
Well mormons will often try to convert you, so if they are smarter than you about religion then they will seem correct to you. They are not! Don't fall for it. I'm not sure what your beliefs are but your best bet is to change the subject when religion comes up. Impress them by having good manners and being funny and smart and nice. Which I am sure you are :-P