Sit down in a quiet place for a few hours to get started. Do your homework and write things down. And, don't be surprised if it will take longer than you expect. Stay away from slogans . Just because it looks and sounds good, doesn't mean it has meaning.
Customers can sense the emptiness of a slogan from far away.
The best you can expect from one is that people will ignore it. Know your competition well . Your customers are shopping and so should you. You need to know exactly how you stack up against other businesses offering a similar service to yours. Know your market.