When you're getting a tattoo, keep in mind that you are totally at the mercy of the tattoo artist. So it's best not to do anything that would make him/her angry or upset.
If your boyfriend or girlfriend is a tattoo artist and s/he is giving you a free tattoo, now might not be the best time to tell your significant other that you're seeing someone else. Or that you'd like to put the wedding off. Or that you think you gave them herpes. Staying clear of these subjects will help to protect you from getting "I am a total luzer" or "Warning: Infected whore; DO NOT ENTER" permanently inked onto your body.
This might sound silly (and for the most part, it is), but when I was getting my tattoo, the artist waited until he was about halfway through and then started asking me if I hated black people--because boy lordy, he sure did. Now, being a bleeding heart liberal, I kept wanting to respond to what he was saying, so I'd open my mouth, then promptly shut it, realizing that pissing off this guy wasn't in any way in my best interest. The tattoo I was getting was on my back, and I would have had no way of knowing if he had decided to add a nice little impromptu swastika to the design (until it was too late), so I kept my mouth shut and just tried to pretend like I wasn't in the mood to talk. (This wasn't a difficult feat to accomplish; the man was jabbing me with a damn needle, so I really didn't want to talk in the first place.)
So, the end result is, I ended up with the tattoo I wanted, but there's some racist tattoo artist in Florida who thinks I have the same whacked-out ideas he does... Also, I spent a good 45 minutes of my life sitting in a chair, scared out of my gourd, desperately praying that the man wasn't going to improvise a little and add the message "David Duke rulez!" to the design. Again, I know this all sounds absurd, but this just underscores the point: You're going to be putting yourself totally at the mercy of the person doing your tattoo art, so for the sake of all that is holy, try to find someone who wasn't as much of a freak as my guy was.
If I ever get another tattoo, I'll be sure to ask all the normal questions (is everything sterile, etc.) and then perhaps ask, "Hey, you don't hate racial minorities or something like that, do you?" Just to be safe.
Fairly interesting update: Oddly enough, when I retold this story at Anml4ixoye's noder gathering in Tampa, I mentioned the location where this had all taken place and panamaus just spontaneously blurted out the name of the tattoo artist involved! In an attempt to convince me that he hadn't actually been stalking me for the last six years, the venerable e2God clued me in on how he knew about this guy: It seems that 'maus, who had been living in Florida for some time, offhandedly remembered hearing a story on the news about some racist tatoo artist (with a faily memorable name) who had just recently been convicted of murder/assault/what-have-you in Panama City! So in retrospect, I suppose the moral of this story is: "if you're selecting someone with the intent of paying him/her to permanently ink a design onto your body, you would do well to check said individual's criminal record first."
This is all totally GTKY, I know; but it still makes for an interesting postscript to the story above.