There are several valuable, practical, and actionable viewpoints offered already. I'll bring a bit more of a long view to the broader question of team building, and suggest some references / best practices that have been incredibly helpful to me repeatedly over several decades.
Startups have a lot of unknowns and a lot of raw talent that is learning along the way. There is a predisposition toward trial and error, when often, in the end, it's easier and less risky to invest your time in understanding best practices and adopt what fits, leaving out what does not fit.
Culture
On this thread, Glenn Nishimura posted: "… it's imperative to be clear on your company's vision and values." Former IBM CEO Lou Gerstner said, "I came to see in my time at IBM that culture isn't just one aspect of the game – it is the game." Defining the Culture explicitly, which includes Vision and Values, is the next step after having a great idea. To learn enough about this to do it well, check out:
1. 15 minute TEDtalk by Simon Sinek essentially on Vision and Values - WHY, How, What.
http://www.ted.com/talks/simon_sinek_how_great_leaders_inspire_action.html
If this resonates with you, drill into his body of work, including his book "Start with Why" or his website http://www.startwithwhy.com
2. Book - Fifth Discipline by Peter Senge (1990 & revised 2006). I read it when it came out and have re-read it about 5 times. It's a great handbook for "programming" a culture that can learn and adapt well because it looks at the context, problems and challenges, from a system theory viewpoint, to invite reflection and response, rather than reaction.
Lifecycle
The people and talent you'll need will depend of course on your situation, but there are some guidelines or generalizations based on studies from the lifecycle of a business. The thought leader in this area is UCLA's Anderson School professor Ichak Adizes.
see http://www.adizes.com
I first read his book in the 1982 and have used it since to figure out what roles are needed and how they evolve at the various very early stages. The website is geared more toward large companies, but if you just study his introductory points, you'll see how applicable it is to startups. Indeed, Dan Martell's post suggesting a certain "great team" is supported by the Adizes' thinking.
To gain a preview of coming attractions of the startup journey and some great practices along the way, I recommend the story of 37Signals.com in the book "ReWork" by its founder, Seth Godin.
To get into the head of an entrepreneur and the emotions, vision, and delusions, as well as to see a great example of "prototyping" I suggest the enjoyable film "Tucker, the Man and His Dream".
See http://www.imdb.com/title/tt0096316/
I hope you find this helpful.
