How do you keep leaves out of your guters

Dad owned a gutter business for years. Products have changed over the years but he sold the crap out of something called Gutter Guard. It was a metal louvered looking thing that laid in the gutter, on top of the spikes/hangers and under the lip in the front.

Very similar to this

http://www.homedepot.com/p/Amerimax...u=100009044&ci_src=328768002&ci_sku=100009044

crap could still lay up on top of it but normally it was not enough to stop the water from hitting the gutter...