"If you're not wearing a pocket square, you're not dressed!" (eSuit.com)

"I believe that a well-dressed man needs roughly as many pocket squares as he has neckties (the corollary to this rule is that the majority of men would be better dressed if they had half as many neckties and twice as many squares)....If a man is wearing a jacket with an open breast pocket, the pocket should have a square in it." (a suitable wardrobe)

How to select a pocket square:

"The pocket square should be the same color scheme as the tie. You should also match the fabric. You wear a silk pocket square with a silk tie." (Los Angeles Times, 1/13/08)

"Generally, you should coordinate similar or same hues of the pocket square against the tie, preferably having the same hues of the pattern on the tie rather than the background color of the tie. If it is a solid colored pocket square against a solid colored tie, then creating similar/same hues of different shade between the pocket square and tie would be a better choice. Alternatively...[you can] match the pocket square shade to the background of the dress shirt, the stripe, or pattern." [Learn more about selecting color schemes] (Men's Fashion Tips)

How to fold a pocket square:

Where to find pocket squares: