It can be quite embarrassing for some parents when a child has a tantrum in public. One of the best strategies in the first instance, is to not worry about everyone else who may be looking, having an opinion or trying to help or judge. The first step is to use a consistent approach to the behaviour - one you would use in your own home. Often if a child is having a tantrum that is not hurting anyone else or themselves, the most effective strategy is to ignore it and let it pass. This may take some time but it does always stop. Trying to reason with an enraged child, trying to bribe or threaten them or yelling at them, is a complete waste of your time. Perhaps as they start to calm down, acknowledging they feel angry or upset because you didn't buy them what they wanted etc., may help them to learn that they could use their words next time rather than having a tantrum.