I used to be one of those people that laughed at people who tapped the top of a recently jostled soda can in order to prevent it from fizzing wildly when opening it (as opposed to just letting it take the time to settle down on its own)
We've all dropped our soda can or been the victim of someone shaking it before giving it to us or something similar. The desire is to not let that slow us down from enjoying the tasty beverage contained within the soda can.
So, I one time, I saw someone tapping the top of his soda can after dropping it, and I was like, "What are you doing?" I mean, how does that have anything to do with the released carbon dioxide from creating pressure in the can, right?
Everything "official" I've found on the topic also says that it doesn't work. This person or that person supposedly did this or that test which never shows any difference between tapped and nontapped shook soda cans. But that doesn't change the fact that it does work. Remember, I used to laugh at people who did this. With basic cola like Pepsi and Coke, I've never had overflowing fizz blow out of the can if I tapped it. Since I started using this technique myself, I have amazed others with full on demostrations.
Of course, there are others who are proponents of this technique.
So basically, I've had nothing but success using this method on regular colas. (I've seen results with A&W Root Beer, and me own experience says that no trick works with it cuz it is designed to foam and foam it does!)