If dust is blocking the air inlet and outlet and/or the heat sink, your computer may overheat. Symptoms of overheating include very hot air coming out of the outlets, an unusually hot base, or the computer suddenly shutting off for no apparent reason. If your computer doesn't have a low enough setting for automatic shutoff due to overheating, the components inside may be damaged.
I broke no stickers or seals while doing this, but there is a possibility of leaving some marks on screws or covers. This almost certainly voids your warranty, so keep that in mind before you start!
This was a very easy process but can present many opportunities for dropping tiny screws. If you have a tendency to drop things or aren't good with screwdrivers, please hire a professional to do this for you.
Step 1: Remove Fan Cover
The three screws circled in red are hex screws. I didn't have a hex driver so I used a small flathead that fit well. Not a great idea, but it worked well enough.
Step 2: Remove Inner Cover
I don't know why these two fans are different. Maybe someone can leave a note and educate us?
The five circled screws are small phillips head. I made extra sure not to drop these while removing them.
Step 3: Vacuum!
I used a small attachment on my regular vacuum cleaner to get most of it, and then a brush attachment to get some of the stickier pieces off. I didn't try to completely clean the fan blades or the bases under the fans.
This amount of dust collected after about 2.5 years of everyday use. Based on what I saw, I'd recommend doing this cleaning at least once a year to enhance cooling of your laptop. Keep it clean!