Where to place side case fan

Hardware Hub Cooling
1

I have a spare case fan on my Zalman Z9 case.

I can only put it on the side of the case as the rest is full up.

Should I put it higher up towards the front or lower down towards the back?

 

2

Put it lower down towards the back, your  graphic card will benefit by the extra cool air rather than something thats in front of the case like a harddrive.

 

3

Into the lower one as intake.

4

agree, it will help your graphics card if you have one.