Unknown to many, tattoo sessions are excellent photo opportunities. This is because of the amount of emotion in the activity. I'm not just talking about the physical pain the subject feels but the "satisfaction" of enduring the pain to get something significant etched on his skin forever. A tattoo session is also fairly easy to cover.
***Body part before the procedure.
***Photo of the subject and artist before the procedure (if possible, showing the "clean" body part to be inked.)
***Design just outlined on the skin.
***Majority of the design colored/filled in.
***Photo of the subject and artist after the session (if possible, showing the inked body part.)
***Body part after the procedure.
Some interesting angles you can (or should) look at:
***Showing both faces of the subject and artist
***Focusing just the artist or the subject's face
***Focusing on the design only
***Full body shot of the artist and subject during the session (depending on the body part to be inked, this shot can be very interesting)
More things to consider:
***Time - tattoo sessions take at least a few hours. Some designs are not even finished in one session. And often the subject and artist just sit still. This gives you a LOT of time to think of interesting angles and effects.
***Gear - tattooist gear are not seen commonly by many people. Take creative shots of the tattooist's needle and ink bottles.
Of course these are just a few things I learned from my experience. As always, nothing limits you but your creativity.
Important! - though you may have the gift of time, you may not have the gift of space when taking pictures of tattoo sessions. Do not get in the way of the inking process! Take pictures but do not bother the artist nor the subject, one wrong move can result to a "permanent" and/or expensive mistake.