Every man should know how to tie a neck tie; it is very lame for a grown man to be wearing clip on ties (or even the zip-up ties that have become popular in the past several years). There are many different ways to tie a tie, and each one has different pros and cons to them. The following is a break down of the three most common knots to tie:
1. The 4-in-hand knot. This is the most widely used knot to tie a tie with; the odds are, if you tie your ties, you use a 4-in-hand. It is the easiest to tie, can be used for many different levels of formality, but is a casual knot at its heart. If you are wearing your tie loose, this is the knot to use. The knot itself is narrow, sometimes to the point of being almost rectangular.
2. The Half-Windsor. This is a variant on the Full Windsor knot (see below); it has an extra step added on to the 4-in-hand knot, so it is slightly harder to tie. It is the most versatile tie knot that I know of, as it can be worn at highly formal occasions, or very casual ones. The Half-Windsor has a definite triangular shape to it, but it is not as wide as the Full Windsor, making it better for standard to smaller sized collar openings.
3. The Full Windsor (also called the Windsor). The Windsor has yet another step added on to the Half-Windsor, resulting in a very wide triangular shape. The size of the knot can make it a bit bulky to use with standard sized collars, but it can be used with them. It is formal knot, but it can be used in day-to-day use, if so desired.
Now that we've covered a little about these knots, time for my personal preferences! I use the 4-in-hand a lot, as I like to do a casual dressy look, but the Half-Windsor has started to push the 4-in-hand's popularity down, for me. I really like the shape of the knot that the Half-Windsor gives, but if you loosen the tie up, it is a little too big for my tastes. I personally don't use the straight up Windsor, the knot strikes me as over-the-top and unnecessarily large, but I am of smaller build, so it can over-power my frame. If you are taller or heavier set, the Windsor could provide the right size knot, and the 4-in-hand's smaller size might cause you to seem larger than necessary. Wearing a suit (and a tie) is all about balance and proportion, so this is something to keep in mind.
Finally, how do I tie these knots? Well, here is an excellent resource: CLICK ME! This link provides a visual and written walk-through of what you will be doing, along with some history of the knots. There are also three extra knots to experiment with, if you so desire.