This one is called the 4-in-hand. This is a slim knot that is good for thin, slim ties.
This is called the King George. This is a pretty thick knot. This one is good for spread-collared dress shirts or if you have a long tie and want to shorten it a bit. A lot of people like the look of this one the best because it gives you the uniform triangle-looking knot.
Shopping for Ties
Knowing how to tie a tie won't do you much good if all of your ties are lame or have Christmas trees on them.
I can't tell you exactly what pattern to look for because there is so much out there, but I can give you some basic guidelines on tie-choosing.
1. Make sure its made of silk. Period.
2. Make sure it feels sturdy. Pick it up and feel it between your fingers, if it is too flimsy and won't hold a dimple, move on.
3. Stripes are good, dots are risky. That isn't to say that there aren't any good-looking ties out there with dots on them, but stripes are usually a safer bet.
4. Stay conservative on the colors. Keep it simple dogg. My favorite tie is a black tie with subtle navy blue stripes on it. Its nothing fancy but it looks good with everything.
5. You'll know it when you see it. When you see a good-looking tie, you'll recognize it. And like with anything else, only buy one or two at a time. You'll end up with a much better collection over time than buying 10 at one time.