How do you safely pierce your tongue?

Go to a professional. Unless you are a trained professional piercer, there is no way to safely pierce your own tongue. You put yourself at risk for irritation and infection, and if you are not careful, Hepatitis. You have a major artery running through your tongue, and if you pierce that, you will have some problems on your hands. Only a professional piercer knows the correct placement of the piercing in order to not hit that artery.