Being non-profit and being tax-exempt are actually two different things, and I suspect what you are actually questioning is being tax-exempt. But here's a quick overview of both; see if this helps.
If you are organizing your group from scratch and want to incorporate it, you incorporate in your state as a non-profit organization. (Or maybe another term--in Virginia, there is no such thing as a nonprofit, only a nonstock corporation.) Each state has its own requirements for incorporation; you would need to contact someone in your state government's corporations office (they have different names) to find out what the process is.
Once you make the decision to incorporate (or not--maybe you just want to be an unincorporated association), then you apply to be tax-exempt. Usually you first apply for Federal tax exemption through the IRS. You'll probably still have to file tax returns, but it's unlikely (NOT guaranteed) you'll actually owe any Federal taxes. Then, or sometimes concurrently, you can apply to your state taxation office for exemption from state taxes--which usually means an exemption from paying state and local sales taxes.
Since you're going to try to pull this together for tonight (!), the fastest way for you to get more detailed and useful information on this is to go to
www.ptolaw.com. It appears that you are down in Fredericksburg, VA (?) so you'll be lucky, because the forms on that site are set up to comply with Virginia law.
In addition, you should also seriously consider joining PTO Today Plus. Their materials walk you though this whole process very well.
Good luck!
