One of the things I learned quickly when I started teaching was that if the students are laughing, they're paying attention, they're engaged, and they're at least partially relaxed. I don't know that I make a specifically concerted effort to get every class to laugh at something every day, but I do try to be silly whenever I can. For example:
- If a student won't stop talking after repeated requests to be quiet, and it's an especially silly kid, I'll be as dramatic as possible and tell the kid that if he won't be quiet, I'll have to glue him to the ceiling and he'll have to stay up there overnight. This invariably makes the rest of the class laugh (and I'm encouraged to do it). It's ridiculous enough that no one is offended for being called out, and the kid is usually quiet (or at least quieter) for the rest of the class.
- When students get frustrated with each other and insult each other (there's one kid in my 5th period class who other kids just don't like), I put a stop to that right away; their insults run along the lines of insulting intelligence or sexuality. (The insults haven't changed; you know what they are.) By being dramatic, I intercept the insults when I hear them and say, "Stop! If you must insult each other, you must be creative about it." This gets them to laugh - they're not expecting me to say that, seemingly permitting insults - and then call each other things like "cat hugger" or "face smoosher" (actual insults used in my classes).
- One kid today just would not sit down; he kept roaming about and desk hopping. Finally, after repeated attempts of having the kid stay put, I said that if he didn't sit down, I'd have to yell at him in German. This immediately got reactions of, "You speak German?!" "Yell at him in German!" (Everything sounds angry in German, even if you say "I love you.") And it focused on unacceptable behavior hopefully without being unnecessarily mean. And it got the kid to sit down.
Of course, I've also been known, in response to students complaining about an assignment, telling them that since I have no life, I like to stay up late at night to figure out ways of torturing them. Sometimes they can't tell if I would actually do such a thing.