Keeping signs simple. But how?

Can a design be any simpler and any more effective in conveying its message?

Sign and design experts have for a long time been arguing that for a sign or billboard to  effectively convey its message, the design should be kept simple. As with many of these suggestions and ideas, you’d be justified in asking for a tip or two on how to do it.

Well, how about this from the French writer, poet and journalist known as Saint-Exupéry (1900 – 1944): “Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.”

Surely a simple but profound technique applicable to so much in life, including design?