This was one of the first lessons I wrote in the first year of my teaching career, and is still one of my favourite ways to introduce pie charts. There's also loads of scope for adding extra stuff in, such as work on fractions and percentages if appropriate for the group.
Pupils begin by thinking of the activities that make up their average day, and use a 24-sector pie chart template to colour-code this. They then look at the fractions of their day spent on various activities. Using a life expectancy of 80 years, they then calculate how many years they spend in total over one lifetime on each activity. To finish off, I've recently added this video to the end of the lesson, which looks at representing the average life as a pile of jelly beans.