The half-Windsor knot is easier than a Windsor knot, but more difficult than a Four-in-Hand. It gives a neat, triangular knot for standard shirt collars and works particularly well with lighter fabrics. And it is suitable for just about any occasion.
Drape the tie over your neck, with the wide end on your right and extending about a foot below the narrow end.
Cross the wide end over the narrow end, and turn it back underneath.
Bring the wide end back down, around and behind the narrow end.
Bring the wide end back up and turn it down through loop around your neck. (See Step 4 and 5)
Pass wide end around the front of the narrow end of the tie from left to right.
Then pull the wide end up through loop.
Push the wide end of the tie down through knot in front.
Tighten the knot carefully, smoothing out any wrinkles, depending on personal taste.
Cross the wide end over the narrow end, and turn it back underneath.
Bring the wide end back down, around and behind the narrow end.
Bring the wide end back up and turn it down through loop around your neck. 
Pass wide end around the front of the narrow end of the tie from left to right.
Then pull the wide end up through loop.
Push the wide end of the tie down through knot in front.
Draw the knot up to collar.