I started off by showing the children 1/3, 1/4, 1/6, and 1/2, and asked them to order them from smallest to largest.
After the inevitable error in ordering, I then drew a pizza with 12 slices on the board, and we worked out together how many slices each would allow.
I then added a few more mixed fractions, such as 2/12 and 7/12, and they ordered these too. Mistakes were made again, but again we looked at how many slices of the pizza each was worth.
This activity was short, fun and was like an arrowhead into the jugular of frustrating fraction lessons!