Do we attach w2s when mailing tax return and what kind of mailing stamp do we use

[MargaretL]

When you mail federal tax return, only forms with federal withholding should be attached. So, if your W-2 forms do have federal tax withheld, do attach them.

The same applies to state returns. Only forms that have state tax withheld are attached to the mailed return. 

You can use any mailing method that you choose, the IRS doesn't require any specific mailing stamps nor method of delivery.