"How was your trip?"
"What did you do."
If your student comes home from our trip bubbling with stories and information, that's wonderful; let them talk and soak it in! If the conversation above sounds more like your experience, you may have to ask specific (preferably open-ended) questions. Here are a few suggestions to get the conversation going.
Talking about the trip is not only fun, but a great way to cement the learning that took place. Take time to ask and listen to your student's stories. You'll be glad you did.