Lots of good advice here, several of which I wished I'd read first rather than experienced directly. Just a couple of things to add:
1. I use neoprene sleeves wrapped over the cam part of the strap to protect the boat. The worst damage I have on my 13 year old boat is from a cam rubbing while on the trailer.
2. If you are using open hooks, make sure to run the strap through whatever you are hooking to so that the hook is hanging, not pulling up. They will loosen when the boat gets softer and it usually seems like it will work down until the tire runs over it.
Show me your OOOOOO face