I mentioned in a previous post that one issue you must consider in the display of a pocket handkerchief is the manner in which you fold it before placing it in your breast pocket. I intend to discuss in future posts a number of possible folds that you may employ; some are quite conservative, while others could be considered flashy. In the end the choice of fold is a matter of personal preference. Remember that part of dressing stylishly involves making clothing choices that reflect your personality.
I would recommend that you avoid using a pre-folded pocket handkerchief. A pre-folded pocket handkerchief is a piece of fabric that is pristinely folded and attached to a piece of cardboard that holds the cloth perfectly in your breast pocket. Using one is akin to wearing a clip-on tie. The problem with a pre-folded pocket handkerchief is that it is too perfect. It lacks the carelessness necessary to be stylish.
Count Baldesar Castiglione in The Book of the Courtier (1528) coined the Italian word sprezzatura which generally translates as "deliberately calculated nonchalance." Castiglione warns that one should "avoid affectation to the uttermost and as it were a very sharp and dangerous rock; and, ... to practice in everything a certain sprezzatura that shall conceal design and show that what is done and said is done without effort and almost without thought. From this I believe grace is in large measure derived, because everyone knows the difficulty of those things that are rare and well done, and therefore facility in them excites the highest admiration; while on the other hand, to strive ... is extremely ungraceful, and makes us esteem everything slightly, however great it be."
When applied to your wardrobe, sprezzatura means carefully making clothing choices so that it appears little thought was put into their selection. In other words you don't want to look like you are trying too hard. A pre-folded pocket handkerchief has that affected and unwanted look. An imperfectly folded pocket square is perfection. That is sprezzatura.