Where in a room should vents be placed for central air conditioning?

In my opinion where the supply vents are located is not as important as where the return air vents are located. the supply vents should be located towards the outer walls if possible. the return air vents should be located towards the center of the dwelling if possible. every effort should be made to get the return air vents as high as possible on the wall , if not in the ceiling.Remember you are trying to get the warm air back to the a-coil so it can be pumped outside through the refrigeration lines to the condensing unit. if the ductwork is used for heating also you should put some return air vents down low to get the cool air to the furnace. This is my personal opinion and may not be everyones.