There are quite a number of different ways that a man may fold a pocket square before he stuffs it into his breast pocket. The so-called "TV fold" is one of the more understated (some would say boring) methods of displaying a pocket handkerchief. The fold's roots can be traced to the pioneering broadcasters of the 40s and 50s. Above is an early photograph of Walter Cronkite displaying a white linen pocket square folded in this style.
To execute a TV fold first fold the pocket square in quarters. Then fold the square diagonally to create a triangle. Fold together the two bottom points of the triangle so that they overlap in the center. Flip the handkerchief so that the remaining point is facing downward and the smooth side of the hank is facing out. Arrange the folded handkerchief in your breast pocket so that about a quarter of an inch of straight fabric is visible above the top of the pocket.