Just remember that only a VERY VERY thin film of paste is necessary... Arctic Silver says on properly lapped heatsinks, where the finish is almost mirror smooth, only a transparent haze of AS3 is necessary.
What I do is squeeze out some onto the CPU core, about the size of the letter "o" on my screen... I use a credit card to cut that in half, wipe half on the base of the heatsink and work it around with a plastic bag on my finger, then use the credit card to spread what remains evenly over the core of the CPU. When installing the heatsink, be sure to set it straight down and avoid any sliding back and forth. Also, with the clamp style heatsinks, you should never install them with the motherboard in the case... I take the motherboard out, use the thin foam padding that comes with new motherboards, and set it on top of that on a table... that way you don't bend the crap out of the motherboard getting the clamp secured, and it does have a little cushion so you don't damage anything. I also install the RAM with the motherboard out on the table.
That's pretty much it... except when I first power on the computer, I go straight to the BIOS into the hardware monitoring section and watch the temps. This is when you want to find out if your heatsink isn't mounted properly... not after you get into Windows, and you start up MBM and see that your CPU is running at 80 degrees C =)
