So, I'm building a gaming PC for a friend, and have 2 120mm Cooler Master Case fans that I'm going to be installing. I just don't know the best place for them. The case it will be installed in is an NZXT M59 Mid Tower case. My first plan was to mount both fans on the top of the case as exhaust fans. But then I remembered that the Hard Drives have no fans. Would it be better to have on fan as an intake fan so it's running air over the 1TB Seagate SATA drive?
You should definitely have at least one fan for intake, and in this case, put it at the hard drive cages at the front.
As for the exhaust fan, it depends on whether you have a tower-style cpu cooler(like the 212). If you do, put the exhaust on top(nearest slot to the back). If you don't, put the exhaust at the back.