In Intro to Computer Science classes, we really start with the basics. Part of those basics is teaching users what exactly is a computer. Many young people have no idea how pervasive computers are in their lives. Once they conceptualize computers, we start to introduce them to how they have to think when they interact with computers, and ultimately write code to tell them what to do. The key point about computers is they take things very literally and precisely. To demonstrate this, we go to a staple of school lunches: peanut butter and jelly sandwiches!
I started to write out a full fleshed out lesson outline, but then I realized that I couldn't do better than an existing lesson plan I've used personally, so I decided to share that one instead. See the TEALS Lesson Plan for a detailed plan. While you are there feel free to browse around because the git book is filled with useful resources.