Before you start be clear about your customer
Take a minute. The world of development is huge. If you don´t have a an idea about your customer stop here. You will waste your lifetime.
The Secret of Success
You know the following things about your customer or at least about your imaginary customer if you don´t have once.
A customer has a problem which you should know.
Would the customer really pay for for a solution?
How long you would have time to solve the problem?
Do you have stakeholders at customers side supporting the project?