Choose and prep the rack
You want the top fat not too thick, and marbling on the inside too. A three-bone rack about two to two and a half inches thick is right. Some people take the membrane off the back; get a flathead screwdriver under it, lift, and try to slide it along to separate it from the meat, then pull. If it rips you will have to repeat it on the other sections. Try not to puncture the flesh.
Cooking at home, it is worth leaving that membrane on. It matters far less than the fuss it takes to remove.