When they answer a question, a student quietly goes to the superhero of day as I call it this year because of my "superhero" theme. They get a pencil from one of my stations, quietly write their name on the ticket and put it into the container with a slot in the top for tickets. It has editable labels for putting each classroom teacher's name, plus editable raffle tickets for writing the classroom teacher's name on (better organization).
Usually either before we get up to do a game, a circle song, or at the end of the class, the person of the day picks about 3 raffle tickets and the students get a piece of candy from my bin. If your school won't allow candy, you could give other small prizes. I am amazed at what I can get out of them AND how much they learn because of the tickets. It is magic. Sometimes, if they do a song or game at the end of class really well, I do a couple more raffles as reward.
EDIT: I now do my raffle at the beginning of class as they are coming in. My person of the day will draw 3 names. If you are just beginning this, you might want to do it several times throughout your lesson or at the end for more direct results, especially if dealing with a difficult class.
BTW- I bought the raffle containers in a 3 pack at walmart and just cut a slot in the top. I just put mailing tape over the label.