You can't have any metal on you, so no jewllery or body piercings. They give you a bag to put them in.
It makes a loud banging noise, a bit strange but they give you a chopice of music to play on the headphones so it sort of sounds like someone's kids banging the wall next door.
If you have an entire body scan it can be quite claustrphobic so I just shut my eyes and hummed with the music, then started making shoping lists in my head. They do break over the musci through the headphones to tell yuo what is going on every 5 mins or so, but it is very odd and if you get an itchy foot or leg, well, you have to live with it!
DH loved my scan as he got a change to talk about electro magnetic frequencies with the man who was operating it.
Oh, and the operators will talk to you as if you are 6 so saying "I have a degree in physics and work in EMC" or similar will stop them talking down to you.
My MRI was for brain tumour and also MS, and then I had one for my back...do ask to see the scans afterwards, they are fascinating.