A can of air can work wonders for blowing off dust and keeping your system clean and cooler. Blowing off dust can easily increase air circulation and unblock vents.
Beware of static electricity by buying anti-static bracelets, or, until then, "grounding" yourself by touching the case door, then the floor, and staying like that for about 2 seconds. This will make you "grounded by the door". It works.