Depends on your case. some of the easier things to look for:
Is your card dusty? can you take a can of compressed air too it and see the mainboard again?
-Dust builds up and makes heat easier to accumulate which can cause some pretty severe artifacts. Ask and i'll show you some of the problems i had back in the day.
What kind of case do you have? does it have a side panel with a vent? better yet, can a fan be mounted onto your side panel to act as a heat exhaust? If no, this could be your problem. Cards are running much hotter now a days.
If you don't have a fan mount on your side panel do you an extra pci slot your not using right below your video card. If that's the case then you may be able to do something with a slot cooler. I don't think they are quite as effective, but i think they still work pretty well. You can mount it under your gpu and have it pull heat from the gpu. Albeit, heat rises, so i dunno how well that works in terms of physics.
i had something else but i totally forgot it, go me