Watch these and learn.
Edited by Mit Namso - 4/8/11 at 6:17am
Don't spread it your self, it traps air. Apply some amount that comes with experience, and let the cooler spread it. You want to maximize the area covered, for best heat conduction across the surface.
And don't make the mistake I did once of applying some, seating the cooler, then taking it off to check, then re-seating the cooler, it leaves trapped air.
If you need to do that, best to clean the chip/cooler, and apply some new amount that you can judge better.