It varies from person to person, a hand tattoo feels more like a cat scratch, where an inner wrist feels like a razorblade. It all depends on the person.
Nothing, the tattoo artists normally taughten then skin so that the needle will not pierce any veins or anything. A professional tattoo artist knows about how deep to go with the needle. The only bad...
A birth certificate or government issued ID to establish identity. That also establishes that you are old enough to join. And a high school diploma, or its equivalency.