Use humor in regard to your product or service. Poke fun at yourself and get your message across at the same time. Humor relaxes us. It invites us to let down our guard and have fun. If you associate your brand with a Jester brand archetype (also known as the Fool or Joker archetype,) you are likely already doing this.
Example: Dental offices are famous for providing dental floss during Halloween trick-or-treating fun. Instead, why not send your clients fake hillbilly teeth as a reminder to maintain good dental hygiene during sweet holidays? For promotional thrust, have your office's logo and contact info printed on any giveaways.