2. Distract
Thanks to their short attention spans, toddlers are actually fairly easy to divert. The idea here is to distract them from the source of their frustration, such as the ice cream they're whining for or the tablet the kid at the neighboring table has at the restaurant.

Pull something interesting out of your diaper bag. Go outside and see if a change of scenery does the trick. Call their attention to the fire truck going by or the aquarium in the waiting area, and you just might be able to head a full-blown meltdown off at the pass.