There is a form that several of us were passing around on XD Talk a few years ago, that I copied and revised for Tennessee specifically and have posted in the Trading Post forums. You will find it as a sticky post.
With some people there is a lot of wailing and gnashing of teeth about how it's un-American to expect them to fill out something like that, how dare you, blah blah blah. I don't want to deal with those people anyway.
I like to have a little CYA involved when I sell a firearm. People have been filling out Form 4473 for years now when they buy a gun new, and have been writing bills of sale for cars and things like that for much, much longer. I don't see the big deal about requiring it, but some people do.
Even if you don't really care about the CYA aspect, you should use the form just to be entertained.