Ambient temperature of the room your in, and your location.
If your in a warm local consider a floor standing case with alot of air volume and addional cooling, especially if you have alot of HD's etc.
Adjust your power saving so suplemental HD's spin down after x time, to cut down on your heat profile.
And service your card, make sure the cooler is clean if its outta warranty strip it down clean your cooler and replace if needed, replace the thermal paste with a good high quality compound ensuring you clean the GPU surface and the heatsink properly before applying.
Make sure all your cables are tidy for good airflow.
Other option of course is water cooling, though if you have a high ambient temperature your still likely to have problems.