I have a new idea of how to do business in my field. How do I keep others from stealing my idea and implementing it in their businesses?

If the method of doing business cannot be patented or the product or service cannot be trademarked or a trade dress established, there is very little that can be done. You can protect insiders in your organization from revealing true trade secrets with restrictive covenants and other agreements but that will not necessarily protect you against third parties.