What do they use to pierced your tongue?

Answer 1

A gun with a needle like they use on ears.

This is absolutely wrong! And actually, you shouldn't get your ears pierced with a gun either, because guns do not come apart, and thus cannot be properly sterilized. Also, at least in the US, working a piercing gun does not make you a licensed piercer. (Claire's, Icing, the Piercing Pagoda, and many other jewelry stores have each of their employees "trained" on using a piercing gun. Many people I know have gone back to a professional piercer to get their ears fixed.)

A tongue piercing is done by using a clamp to hold the tongue in place and provide guidance for the piercing needle. The piercing needle (which should be opened from a sterile pack in front of you) is then slowly but firmly pushed through the tongue, while the piercer pays close attention to your body language to make sure no nerves are damaged during the process.

If you really want the full details, call your local licensed piercer, and he or she should be able to give you all the info you need. If not, that's not the person you want poking holes in you!