I tried to search the sub for an answer to this question, but I had trouble finding an answer from the client/subject side! If there is a post, please lmk and I can delete this.

I have gotten involved with a club at my college and we often take group photos. The director of photography always wants a nice smiling one and a "hehe haha" (as she calls it) picture where we fake laugh at each other. How do I make it look realistic? I feel like I always laugh once and then put my head down because I feel so silly looking. Is there a secret or is it just confidence?