Best place to put my case fans?

[willbsp]

My case is an Enthoo Pro M. I am unsure as to where I should put my case fans for the best airflow, I already have two 120mm fans in the front (I have a disc drive installed) and one 120mm in the back. The front ones are intakes and the back one is an exhaust. I still have two spaces up top for 120mm I want to make them exhausts but that would create negative air pressure. So should have 1 fan on the top as an exhaust, 1 fan on the top as an intake, 2 fans on top both as exhausts, 2 fans on top both as intakes, or 2 fans on top; one as an exhaust and one as an intake. Also, could I change the rear fan to an intake so as not to create negative air pressure?
I am, obviously, new to all of this.
Thanks

 

[Aeacus]

Since hot air rises, the rule of thumb in case airflow is as follows: front and bottom - intake; rear and top - exhaust.

In your case:
Front: 2x 120mm - intake
Rear: 1x 120mm - exhaust
Top: 2x 120mm - exhaust

If you don't want negative pressure then you have 2 options:
1. Set your intake fans spin faster than your exhaust fans.
2. Only mount one 120mm fan at the top as exhaust.

Though, for best cooling, the negative pressure is better than positive pressure.
Further reading: http://www.tomshardware.co.uk/faq/id-1858957/airflow-101-setting-fans-keeping-computer-cool.html