How do you keep leaves out of your guters

my bosses house has the screen crap on it and i cuss all the time when i have to clean them out because its not leaves but deteriorated leaves stuck in the bottom. Eventually the gutters get filled with a mud like substance. The screens scrape your hands all to hell and leave you begging for mercy. Also the screens get messed up and do not stay on the gutters very well and you fight longer with the screens.

There was a product out there that covered the gutter but the water would still flow inthe gutter but i have no clue what it was called.

remove the gutter or clean them out yearly as maintenance.