I discovered a formula to make an audience laugh. It is possibly too simple to be useful but here it is. The apparency is, present your audience with a bit of reality and then change it, turn it round. The reality is you notice something that will be real to the audience. Then you imagine a way to turn that round, perhaps into some form of opposite, and present that to the audience. Then turn it back into what you noticed in the first place. It is possibly to do with getting the individuals to hold two opposing ideas in their minds at the same time. It is reinforced if it has direct relevance to the audiences experience.

A joke is a formalised, prepackaged version of the above. It will have the two opposing realities but not always the direct relevance to the audiences experience.