How to define the target customer to develop a successful marketing plan for your business?

You can not answer that until you define your target customer. This is where most businesses fail. They have no idea who actually purchase (or to buy) its products. They only want to sell to everyone.

So ask yourself,

First: Have you designed a product that could potentially new corner a new market segment, does a lower price that undercuts its competitors, their products are much better? What is your hook? Why customers should buy from you instead of someone else? Who is trying to sell? Is anyone who reads magazines or websites? Or do you mostly sell to repeat customers, who then contact your company by word of mouth to your partners? Do your products are unique and should be shown the picture, or are so familiar to potential users that you can use the text? And where your potential clients general information about your business?.

Consider this

These are the principles of the thousand questions that will develop a good marketing plan.