Warmups are always good for getting the kinks out. it is like stretching before running. Here are a few I've done recently.
I think the really tricky part is to remind yourself that no one has to see these. I tend to erase sometimes and there is no point, so move to another piece of paper and leave that crappy drawing right where it is. It lets you get more comfortable which leads to thinking less.
Of course I say no one will see it, but then I post it here. oh well, you can see my suckiness and feel inspired :-)