Begin with the necktie around your neck, seam against your body. I will refer to the two different sides as the fat side (the part of the necktie you ultimately want showing in the end) and the skinny side (the part which will be covered by the fat side in the final product). Begin with the fatter end on your left side and skinnier end on your right. Ensure that the end of the skinny side lays at about belly-button height.
First, simply cross the fat side over the skinny side approximately over where the second button from your neck of your shirt would be.
Next, pull the fat side up behind and up over the cross you just created so that the entirety of the fat side lies on top, with the seam against your body, directly in the center of your chest. The skinny side should also still have the seam down, and be just slightly to the left of the center of your chest.
Near the knot, pull the fat side of the tie to the left side of your body, still on top of the rest of the necktie. The skinny side should now be at the center of your chest.
Pull the fat side of the tightly across the back of the knot. You should have a right angle between the fat and skinny side. The skinny side still should not have moved, and the fat side should have the seam out, being held in the air on the right side of your body.
Stuff the fat side through the hole between your neck and the knot tight against the knot. You should now have both sides down the center of your chest. The fat side should be right against your body with the seam facing outwards, and the skinny side should be directly against the fat side. The seam of the skinny side should be directly against the fat side.
Next, simply bring the fat side to the left side of your body like you did earlier.
Pull the fat side of the tie fairly tight across the front of the knot. The skinny tie has not changed positions and the seam should still be against your body, in the center of your chest. The fat side should again create a right angle with the skinny tie, this time with the seam against your body.
Pull the fat side of the necktie up between your neck and the knot directly in the center of your body. The fat side should be pulled through entirely so that it can lay, seam down, in the center of your chest, with the skinny side behind it.
With your right hand lift the very bottom of the fat side of your necktie up towards the top of the knot. Using your left hand, very slightly loosen the very outermost layer of the knot.
Pull the fat side of the necktie between the outermost layer of the knot, and the rest of the knot. Pull the entire fat side of the knot through with your right hand, while pushing slightly upwards on the knot, to ensure a tight knot.
Finally, with one hand simply pull down on the skinny side (behind the fat side), and push the knot up to tighten against your neck with the other hand.
If the end of the necktie is not between your belly button and the top of your belt buckle, begin again. When beginning again if you needed a longer tie, have the end of the skinny side begin slightly higher than your belly button. If you need a shorter tie, have the end of the skinny side begin slightly lower than your belly button.