The real answer is when you speak in tongues, not that anyone seems to care in this religous site Acts 2:4 / Acts 8:17 / Acts 10:44-48 / Acts 19:6.

Acts 2 is the result that Jesus wants, not only feeling it but using it, romans 10 : 10 confessing means to say the same thing, when speaking in tongues we are speaking Spirit encouraging ourselves to be led by God.