When my son was growing up, we measured him just inside his closet and kept track of his growth spurts by writing the date and height on the wall. Big mistake. You can’t exactly take the wall with you when you move, and if you paint…. Well, you see what I mean. Here are a couple of links to growth chart tutorials.
I found How to Make a Growth Chart over at How Does She. She actually cut those cute toppers out with a band-saw, but if you aren’t handy, I bet you could find something in your local craft store and just hot glue it on the chart.
Over at Cobwebs, Cupcakes and Crayons you’ll find Little By Little, Inch By Inch: Making A Measuring Keepsake.