Even Mae West would probably be frustrated with the quality of the average business plan I see! I'm amazed at this, since "how to write a business plan" is no doubt the most frequent topic found in every business journal, every web site for startups, and the business section of every book store. You can get free download business plans from the Internet, and there are thousands of customized samples for sale highlighting every business area.
What is the definition of a good business plan? In simple terms, it is a document which describes all the what, when, where, and how of your business for you, your cohorts, and potential investors. There is an old saying that you do not fully understand something yourself until you write it down. Forcing yourself to write down a plan is actually the only way to make sure you have a plan.
Make sure your plan answers every relevant question that you could probably imagine from your business partners, spouse, and potential investors. That means skip the jargon and include explanations and examples. A plan that generates more questions than it answers is not a good plan.
Finally, hone the result into a professional document. Remember that you only get one chance to make a great first impression. Make sure it has a cover page, table of contents, headings, page numbers, and is organized logically. If I see ten different fonts and text sizes, I'll conclude that this is a cut and paste hack job. If you skipped the spell check and proofreading, I'll assume you probably will show the same inattention to running your business.
So what if you know that you simply are not a good writer, or do not have the time or patience to write? No problem. That's why they invented ghost writers, and came up with the concept that you can pay someone else to do it for you. It's a small price to pay for a successful business, or for that $ 1M investment you expect the plan to entice.
The tougher case is where you really do not understand the business you are about to enter, so you do not know what to write. This is a recipe for failure that most investors and professionals can quickly see, so no investment will be forthcoming, and your business will likely wither and die.
My advice here is to swallow your pride, and find a partner who has the "domain knowledge" and the business experience to get you going. Your idea may be right, but dead right is not very satisfying to anyone. Other alternatives are to spend some time working in a related business, sell your idea, or give it to someone who hopefully will remember you as the new business flourishes.
Notice that I did not say anywhere that a good business plan has to be at least 20 pages, or have 10 sections, or must start with an executive summary. These are good things, but I've seen great business plans that are ten pages, or have totally non-standard formats.
A great business plan is one that you are proud to distribute, your team can learn from, brings investors to your door, and would even impress Mae West . As she might have said, "Send one up to see me sometime!"