Tattooers: how do you deal with shaky clients?

I'm an apprentice tattooer, and I did my sixth tattoo today. My friend would not stop VIOLENTLY shivering the whole time. I know that getting used to this sort of stuff and working around it is a huge part of being a good tattooer. I was wondering if anyone had advice they'd be willing to share. Do you just hold the body part still the best you can? Do you pull lines faster or slower? Is there any technique that works well for you?