How long should a tie be?

The tip should reach the middle of your belt buckle when standing. Too short reads careless; too long is equally noticeable.

What tie knot should I use?

A four-in-hand for most collars and everyday wear; it is slightly asymmetric and sits well. A half-Windsor for spread collars and more formal occasions.

Can I wear a knit tie to the office?

Yes. A knit tie reads slightly more relaxed than silk and works well in smart casual settings, particularly without a jacket.

How do I match a tie to a shirt and suit?

Keep one element patterned and the others plain if you are unsure. A patterned tie with a white or light blue shirt and a solid suit is difficult to get wrong.