What way should fans be place.

I'm thinking that my 120 mm fan in the rear of the case should pull the warm air out of the case or does it need t push fresh air into the case. Same with the side fans do I push cold air in or pull fresh air in?

At the side will be one 90mm fan that cool the GPU now the gpu already has a fan so I thing the 90mm should push cold air in the case?

Any ideas or should I just experiment.

Not in the mood for cheese?
That excuse has more holes than a slice this fine Gorgombert!