A bit of History:
Why the hell is this knot called a Windsor?
While many think the knot was created by the ever-stylish Duke of Windsor (the one married to that American!), it was invented by his father, George V. He preferred a thicker knot and had his ties made with a thicker fabric to result in a wider knot. The Windsor knot was then invented to replicate the thickness while using thinner fabric.
Why a Windsor knot?
The Windsor knot just looks more professional. Sure, if you are going to a hipster concert and want to rock a skinny tie, by all means, give it up to a half Windsor. But at work, cocktails, dates, the full Windsor knot is the star.
Here, Alex provides a step by step on how to tie the handsomest of knots.
The shorter end of your tie should sit a little higher since you will need much more silk for this style of tie.
Cross the larger side over the smaller and bring that back to yourself.
By threading it over the top you are creating the small triangle that makes the base Windsor knot.
(To make a skinnier, single Windsor you can stop here and cross over and create the tie from there)
Go back over the triangle again so it makes a larger triangle.
Pull the large piece through the triangle.
Thread the larger end through the bottom.
Pull the silk. Do not strangle it! Pull the shorter end to the top so the tie sits beautifully.
Windsor knots should always be worn with a spread collar or a cutaway collar because of the symmetry of the triangle of the tie with the triangle of the collar.