It may be different in the US but in Canada the first step is to do a name search and register the name of your non-profit and the second step is to register as a non-profit under the Society's Act either provincially or federally depending on the geographic region you will be serving. Both will be for a nominal fee.

This process requires the applicant to answer the kinds of questions Tim listed. They essentually become your Constitution and By-Laws. You will need to identify your founding members, board of directors, roles and responsibilities, meetings etc..

I agree with Tim that running a non-profit is very similar to running a business and therefore a solid business plan (long term strategic (5yrs) and short term operating (annual) plan) is very important.

There is a lot of movement towards mobilizing non-profit organizations to engage in social enterprising to generate revenues to support the work of the non-profit. For example a drop-in youth centre may operate an ice cream shop. An arts council may run a gallery gift shop with all of the profits going back into the society to operate its programs and services. The social enterprise may be staffed by volunteers or it may create jobs and provide job training. Social enterprising allows non-profit organizations to be less dependant on grants and donations and therefore less restricted by external criteria and more indepentantly sustainable over the long term.