Assuming everyone will buy or having no idea who will by and defaulting marketing to all is a big reason why you will fail. Understand that only a small number of people will actually purchase your product or use your service.
You must determine what or who your target market is. Ask yourself "Who will buy your product or service"? Now before you answer this is specific, not general. Lets say you sell all natural makeup. Now just because you sell makeup does not mean all women will be interested. Fact is some have absolutely no interest that it is all natural. So who do you know that does? This does not mean you won't reach a broad demographic over time. You just have to narrow your target.
Knowing your target and zeroing in on this specific group gives you a niche. You are now an expert/specialist. This will allow for narrowing it down even further. Why would someone want to purchase your product or service?
People purchase products and/or services for 3 reasons -solves a problem, satisfies a need, just to make them feel good. Take a moment and determine which of these does your product or service provide first. Your product or service may serve more than 1; even all 3.
Now turn your focus to the demographics. Break this down to target age, gender,lifestyle, social class, beliefs. You can break this down even further. Before you resist, WAHM has work in the title. This does not just happen. If you want success you must do your research.
Now that you have the demographics portion down, how will you market to your target? Internet, newspaper, parties, word of mouth, fundraisers, etc. Now match that to your target market. Count the people you have come in contact within the last month. And yes I mean literally count as in 1, 2, 3. Out of the people you know, and you should (this is called networking), how many are in your target market?
You have the numbers so now figure out how often will they need to buy? Once a year? Once a month? Can you sustain and build a business off this information? If not, you will need to start over in your business plan but you will have the information for a better start.
A little homework goes a long way. Don't be afraid of it. This research will give you a realistic view of your business future. Just because you love the product or service does not mean everyone will. Its better to find out before you invest a large amount of money into a failing venture.