Que has hecho? Print out this activity, and have your classes practice asking each other questions like, "Has visto un oso polar?"
If they they have, they'll say, "Si, he visto un oso polar!" and then they'll sign their name in the blank for that space. If they say no...then the student who is doing the questioning will ask different questions from the grid until the person he's speaking to resonds with an affirmative. That person will then sign the paper. The goal is to have them speak to everyone in the class (if they can), collecting MANY different signatures!
It's a quick (10-15 min) activity that gets your students up and about. EDIT the page to suit your vocabulary needs!