Cub Scout Pinewood Derby - Help Wanted

My first grade son and I are getting ready to build our first Pinewood Derby car. I've been trying to read anything I can about them (the cars, not first grade sons), but would appreciate any advice you might have in the Comments box. We're not obsessed with winning, but you don't want a clunker either! My main concern is that for all of the speed tips out there, it seems everybody has a story about someone who just nailed the wheels to the block and took first or second place! Any advice/tips are much appreciated.