Imagine a situation when you have to code something which will also be visible to the user. One of the option is just to start coding and to see if it will work for customers and result is quite good enough. And I go that way often myself - start to code for a final result almost immediately.
Recently I discovered that may be there is a better way. I was checking out the The Foundation’s a business program and found the idea about pre-selling software which may be helpful even on a such low level of the software development when you have to add some feature to the project.
I was so inspired with pre-selling that I tried to “sell” my prototype to the boss. Funny thing about it that he thought that I already implemented the feature because the prototype was looking like a screenshot of real software.
After successfully selling the prototype I implemented the feature and everybody was happy.
Bottom line: Try to sell first what you want to do to your customers, boss, family or friends.