I want to run a sign writing business and need to know how useful is a sign for a business.
A sign is another form of marketing for a (brick and mortar) business. As a minimum, the sign should have the name of the business. Depending on its size/purpose, contact information, logo, and a tagline might be appropriate as well.
The sign’s color, size, shape, and contents should likewise reflect the business “brand”. All materials that a business uses for its marketing should have a similar “look” in order to create marketing synergy.