The "Search The Community" bar on the right-hand side of the page is a useful feature, particularly for questions like this that come up fairly frequently.
Here's a recent discussion of the same topic:
http://cs.finescale.com/fsm/modeling_subjects/f/16/t/155273.aspx
I prefer the heat method, but I've also had good luck just gently drawing them between my fingertips, imparting a little curve each time. It's important to go slowly, so as not to overdo it.
Cheers