How can I adjust my thermostat to account for solar gain?
Regarding the cooling problem: first, I presume it is a forced air system which should have some dampers in the cool air ducts. Try partially closing the dampers (2/3 to 3/4 closed) in the ducts that carry the air to the shady side rooms. A similar effect can be made by closing the floor/wall/ceiling vents on the cool air ducts. (This is essentially what Isherwood recommended.) Additionally, set the fan to manual to keep the air circulating all the time. This will help even out the temperature throughout the house by mixing the air from all the rooms.