post any methods or thoughts that may prevent dusts in pc case, im a lazy person most of the times... so i've been trying to think of methods to prevent dusts in the case.
I use an Antec Sonata case which comes with a removable (washable) dust filter on the front over the primary air intake. It works fairly well for normal sized dust particles and keeps me from having to clean my large Zalman CPU fan too frequently.
Check my site for pics if you're interested, as well as links to the product information at Antec.
There is a secondary air intake near the top of the case used primarily to supply cold air to the power supply directly. Contrary to some reviews, it works very well and quite a bit of air does move through these holes in the top-sides of the case. Unfortunately, they are not filtered, so grab some filter material (nylon works well; check women's department at the store) and duct-tape it over those holes on the inside.