What i need to make a fan controller

Yeah, you could do it that way. Personally though I'm going to build a voltage regulator based on the information on this link. I'd like to control more that one fan with this circuit. I've also seen a kit that has everything you'd need including a circuit board. Where you'd get that just now I don't know, that link must be on my other computer, I'm "on the road again" and on the laptop.

In order to help you any further on just using a potentiometer I'd need to know how many amps that fan draws. That information should be on the fan's label.

it draws .26A at 12v

but what kind of pot would i need?

haha...

Oh boy, did I screw up my first design. I'm suprised no one else caught it. Anyway, I up loaded a corrected drawing.

Or you could purchase one of..these..they work fantastic and have excellent voltage control for such an inexpensive unit.

If you wish to remove the logos and such from the front to have it all plain black just use some acetone on a rag and a little elbow grease. They look sweet installed then (I like the lean and clean look)