Project starts with business requirements analysis. It's pretty much like asking an architect to draw a blueprints of the house before construction starts. This guarantees that job will be done right, in time, within budget and have strong base and enough flexibility for expansion.
Often people come up with general idea of web site they want, but before you even start programming, you need to create a good plan of what features will be built, what architecture of the software will be, should it be custom made or can use out of box packages and products. All those questions are answered during business requirements analysis stage.
Having good plan before you start will ensure that software you are getting will do exactly what you want it to do and exactly in a way it should be done. Also it's good idea to plan future growth and think about possible features, so product will be designed to expand as your business growths.
