First- try to clean out the exhaust fan(s) with some compressed air. Make sure to turn off the computer first! (i also saw somewhere that you should stick a small toothpick slightly in the vent to prevent the fan from spinning as you blow the air in).
next - you could either lift the back of the laptop off the desk with something like a notebook (idea is to get more fresh air under the laptop), or buy a laptop cooler (basically a stand with a fan underneath blowing fresh air up to the laptop's intake)
Lastly- you could TRY to redo the thermal paste on the cooler but this is a whole process