There are actually several steps to forming a non-profit corporation. The first is to file a "certificate of incorporation" with your state’s corporate filing office. You will want to specifically fill out forms that tell the state you are applying for the status of a non-profit corporation. The state should have guidelines to help you with this process but you might also want to consult a commercial business attorney who can assist you with this process.
Even after your filings have been approved by the state’s corporate filing office, your corporation does not automatically achieve tax-exempt status under the state and federal government. You will need to separately apply to the IRS for federal tax exemption as well as state tax emption in a few states.
You will first want to file a 501(c)(3) tax exemption application with the IRS. Make sure you have already been approved by the state as a non-profit corporation before you file the application because you will need to also submit a copy of your filed certificate of incorporation along with the application.
While in most states you will be automatically granted state tax exemption status along with your federal tax exemption status, you will have to file a separate application for state tax exemption if your corporation is located in California, Montana, Pennsylvania or North Carolina.
The first thing you will need to do is define some kind of structure for your non-profit corporation. You should create rules and procedures ("bylaws") for electing directors and officers, voting, and making other kinds of decisions.
After your non-profit has a structure, start appointing directors and having directors’ meetings in order to determine the direction your non-profit. Also, be sure to apply for any permits or licenses your non-profit might need to accomplish what it is setting out to do.
When going through the application and organizational process of forming a non-profit, you will probably want to consult a business attorney who has experience in dealing with start-up companies and specifically with non-profit organizations. Your attorney can help you to understand and fill out filings for becoming a non-profit corporation, as well as applications for tax exemption status.