What will you do if you toddler throws a tantrum in public places?

Hui is very right when she says that you do not need to be embarrassed. What I would suggest is let the kid vent out and try not to lose your calm. The kid are smart enough and know exactly how to get things done their way. If you do not give in to their tantrums, they will automatically learn that tantrums have no effect on you and will stop in the future. Letting tantrums go on for a longer time once is way better than tantrums happening every other day. Also, as Deepshikha points out do not hit/insult your kid in public!!