If you have kids and watch Play School, then you'd certainly do that!
I was asked this week to make a train cake for a little boy's birthday. I wasn't sure where to start with this cake, but I knew it was going to be cartoon-style... So, I started with a cartoon setting: Blue sky, and green hills. I knew that I was going to make steam 'clouds' getting bigger and bigger, come out from the train (a lot easier to draw cartoon-style as well), so made those out of flower cutters, and then just with a knife for the biggest steam cloud:
(though it took a lot longer than it appears)