I have the unusual distinction of being a programmer in a business school that is currently experiencing something of a startup fever. Penn also happens to have a relatively small but enthusiastic CS community in which I consider myself active. One result of these circumstances is that I am frequently approached by students1 who have ideas for a business or have started a business that requires a website, but who have no idea where to start. I've been on the other side of that table too, hiring contractors for startups I've worked on. Here's the basic outline of how I answer this common question.
How you should accomplish getting a website built depends a lot on how fundamental the technology is to your business, how complex it is to build, how much money you have to spend, and what tradeoffs you're willing to make between quality and time.