"Try to choose actions causing high total net utility gains when summed over everyone affected."

is an attempt at a 15 word summary of:

Precedent Utilitarians believe that when a person compares possible actions in a specific situation, the comparative merit of each action is most accurately approximated by estimating the net probable gain in utility for all concerned from the consequences of the action, taking into account both the precedent set by the action, and the risk or uncertainty due to imperfect information.