I always think it is most important to learn common knowledge. common knowledge is the things that is really obvious to all natives, but is different depending on your country. this could include pop culture and music, some basic historical events, what is polite versus impolite, or what is funny.

When I visit foreign places, I love to see what the locals do. It's nice to go where tourists go, but I prefer to hang out with the local people. Eat where locals eat, even cook a good dinner at home. Shop where they shop. Getting a bunch of locals over for a cookout or something. And just like Cammie said, understanding the culture, what she called, "common knowledge". It would be a very good idea to pose to your guests, too! There may be something specific they want to do or see.