Tattoos do hurt more where there is bone, but they are not that bad. Take something along to focus on, music, a picture, a friend. Talk to the artist. Something to distract you from the actual tattoo. For me, it was not so much the pain as the sound of the gun that got annoying. Plus, the tattoo needles only go half as deep as a hair root is. It hurts less than plucking a hair!
Actually, There is really no way to prevent pain while getting a tattoo. Just don’t watch during the process of designing the tattoo and relax. And for decreasing the pain you can use ice or pain-killer after the process.