CPU fan question

I'm setting up the Prolimatech Megahalems Rev.B CPU cooler, and I'm not sure which way to install the fan. Should it be on the side of the cooler facing the back of the case, blowing air off of the heatsink out the back of the case, or should it be on the side facing the front of the case, blowing cool air onto the heatsink? Any help would be greatly appreciated.

The fan should be blowing air through the heatsink out the back of the case. The fan should be blowing air over the heatsink and out the back. If your case has a outtake fan on the top of the case, blowing the air over the heatsink out the top is better. If you don't have a top outtake, blow it out the back.

Thank you all for your input. Because I have fans on the top of my case, I'll reposition the cooler so that it has a fan blowing through the heatsink out the top, and one on the other side of the heatsink also blowing air up (push/pull). The reason I could not do this before was because of rediculous size of my heatsink (Prolimatech Megahalems are massive) blocked two of my RAM slots with a fan attatched on that side. But it's good to know I can flip it and have it blowing out the top.