The pocket square is an item that I feel some men have trouble getting into as they reach the age where they begin to dress more formally. Reasons for this could be anything from the wearer thinks them to be flamboyant, to they simply don’t know how to fold them. As for as pocket squares being only for the flamboyant, nothing could be further from the truth. A pocket square can be as understated and conservative or as loud and exuberant as the wearer wants them to be.
When trying to decide what color pocket square to use remember that you cannot go wrong with white. A simple white will add another piece to your over all style without taking any risks on putting patterns or colors together. By simply folding his white pocket square, creating an thin crisp line above his pocket, this gentleman succeeds in adding interest appropriate for even the most conservative and formal event.
Colors and patterns can also be used with great effect but fight the temptation to buy prefolded or matching tie and pocket square sets. These may seem to be ideal but they create a boring look and are best left to the novice dresser.
Choosing a pocket square that you like with your ensemble can be difficult partly because there are no real rules. Some men will coordinate colors with their tie or shirt but contrast patterns while others will do the opposite. Some may pull out a minor color in their shirt or tie with a pocket square, while still others may pair it with their socks or cuff links. Just put some thought behind it experiment a little if you need to. Before long you will fall into a combination that is all your own. This gentleman succeeds in creating an memorable style by contrasting patterns and some color in his shirt, tie and pocket square. He allows this combination to really stand out, without looking over done, by pairing it with a subdued cream jacket.
Materials can be anything from silk to linen to cotton but its not for wiping your nose. That is what the handkerchief is for and you keep that in another pocket.
For some basic pattern and color mixing guidelines see Mixing patterns in your suit, shirt and tie.
Here is a great resource for folding pocket squares from Sam Hober.