As you have been doing your research and talking to other people who have made successful applications in years past for tax-exempt status, you have no doubt heard the term advance ruling. An advance ruling was a process by which a very new organization lacking years of documentation could obtain its favorable determination and then have five years to show that it was a publicly supported organization. At the end of those five years, the organization had to file another form showing that it met the standards and should be granted a final determination.
As of 2008, the rules changed for the better. The advance ruling process was eliminated. You still need to plan for and show in your budget that your organization is indeed a public charity. If yours is a relatively new organization and does not have a multiyear history of receiving public funds, you need to show in your narrative and in your budget that you can reasonably expect to be publicly supported. You must meet that one-third threshold before the IRS will accept that you are a public charity.
The IRS will now accept that you are a public charity based on the documentation you provide. You must meet the established one-third threshold for five years. With your sixth taxable year, you must file your yearly Form 990, showing you meet the public support test.