I've had more than 12 so I have it down to a routine:

I take my own earplugs because they are the soft comfortable kind.

I take my own slipper sox because my feet get cold and shoes are uncomfortable.

I also take a thermos of coffee to drink on the way home. I shower and wash my hair but don't bother drying or styling it and no styling products.

I ask for a blanket because those tubes are cold and I ask the tech to please let me know what she is doing which calms me.

Oh yeah; tell them you want a pediatric needle.

Hope that helps.