As you can see above, everyone has their own opinion so it's up to you to decide! Here is my take on it, which is similar to what's on the ASilver website.
No complicated procedure required - it'll make no difference to the end result as many who have taken apart PC's will know.
For older exposed cores without a heat spreader, a small amount on the core which is then spread out into a thin layer works best. No need to put anything on the heatsink - pressure and heat cycles will do that for you and it'll work itself evenly into both surfaces. This makes cleaning the CPU at a later date much, much easier as it doesn't spread down the sides of the core.
For modern CPUs with heat spreader, a small rice sized blob directly in the centre works best and again nothing on the heatsink. When you apply the heatsink, make sure it's not at an angle. Press it straight down, then attach the clips. The pressure will spread the paste evenly outwards from the centre. You can give the heatsink a small twisting motion if you want (if it'll move) to try and force any air bubbles out, but I don't think it makes any difference.
When I've removed heatsinks using the above simple method, the paste had formed an even layer above the CPU core and on the heatsink, but not spanned out beyond the edges of the heat spreader. Again, this has all the desired effect, but makes cleaning the CPU much easier than having paste going over the edges.
Spreading paste all over the heat spreader manually is in my opinion pointless and messy. You're not going to get it as even or as well displaced as letting pressure do it for you and there are more chances of bad contact spots - something you're using the paste to avoid! Plus it's harder to clean off all that paste.
