Ask the same 20 questions year after year (1-18, but probably age 3 or 4 is a great age to start) and see how your child's responses change year to year. Makes a great keepsake to give to them when they turn 18.
Last year for my kid's birthday, I found this on Pinterest and decided to create my own Printable version. You can print and write in your child's answers or I created the PDF so that you can just type in their responses, save and print. Download your Annual Birthday Questions here!