This is also known as: How to Avoid Getting Nasty Letters from the Zoning Officer
The first thing you need to know about signs is that most signs require permits! This includes all changes to signs.
The second thing you need to know about signs is that we are only talking about signs visible from the street or public right of way. They don’t count if they can’t be seen from the road.
The third thing you need to know about signs, is that if you are a non-conforming use, such as retail, in a residential zone, your ability to have signs will be greatly restricted and much of what is discussed on this site will not apply.