The width should be approximately the same as your coat lapels. The best materials for ties are silk or a polyester and silk blend. The tie should be lined with a stiff material to give it body but, before buying, make sure it ties into a good knot. Avoid anything too bright. Colors should not clash or be so monotonous that they fade into each other.
Some contrast is necessary.
Texture is the look of the materials, and they should be compatible. For instance, a very shiny silk tie will clash with a wool suit. Styles should be compatible. A wide tie with narrow lapels looks strange. They should be highly polished and in good repair.