How do you know if you have a clear business plan? See if you can answer these three questions.
Question 1: Who are your clients?
A common answer is "everyone", but that's never true. Your audience needs to be well defined and specific. If you don't know who they are, you won't know where to find them. The more you can clearly explain your target audience the more successful you will be.
Question 2: How will you reach them?
A solid answer to Question 1 is critical to be able to determine where your clients are. If you don't know where they are you cannot plan any specific way to reach them (aka Marketing Plan).
Question 3: Who will pay you to provide your service / product?
This may seem like a question with an obvious answer, but it's frequently not so clear cut. For example, if you are starting a website that provides a free service (like a Lifestyle Guide or a Weather Website, etc) your users will not be paying you to provide your service. So the answer to Question 1 and Question 3 are not at all the same. In the examples the clients are the people who will want the information you are providing, but the ones who will pay you are likely Ad Placement Services. Sometimes the most valuable product you provide is the audience you build.
If you can clearly and specifically answer these 3 Questions you are well on your way to launching a successful business!