+1 on Meguiar's Plastx X. Never had a problem with fogging headlights after that.

 

If you have a Porter Cable or Flex, hit it with a light polish then a sealant or wax. If you don't, buy some Adam's Revive Polish, apply by hand with a foam pad and you will see the haze coming off on the foam pad itself. After, buff off and apply a coat of wax and you're good to go. The pad is white, polish is blue, and you can see the pad is now yellow from the haze coming off.