There's no one-size-fits-all answer to this question, as the best way to write a startup business plan will vary depending on your specific business and goals. However, there are some basic elements that all good business plans should include:
An executive summary that outlines your business, its purpose and its goals.
A detailed description of your product or service, including how it is unique and how it will meet the needs of your target market.
A marketing plan that explains how you will reach your target market and promote your product or service.
A financial plan that outlines your revenue and expenses, as well as your short- and long-term financial goals.
If you're not sure where to start, there are plenty of resources out there to help you, including templates, sample business plans and advice from experienced entrepreneurs.