Equally important - attach the boat securely to the ground. Various suggestions have been made here before. On sand you can easily bury a piece of wood with a line on it. On grass you can use an earth anchor, something like this - http://www.acehardware.com/sm-anchor-eye--pi-1275470.html

I'm not the only one here who has had a boat go over with the mast up in a storm. <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" />