The computer you use can get pretty dirty sometimes and that might reduce it's performance and reduce it's life time so here is some advice on how you can clean it up.
The computer won't be well cleaned if you'll use alcohol cleaners, you'll need to use a hard surface cleaner, in concentrated solution in warm water.
Cleaning case You'll need a cloth that you'll wrung in solution you chose. Use this cloth to wipe casing and all external parts (cabling, keyboard). Make sure you wash cloth since soil will be considerable. Excess water shouldn't be used and try not to let water go into vents of case. You will be able to clean between keyboard keys by using damp cloth pushed between keys with toothpicks.
The following actions need to be taken every six months. Cleaning actions that should be taken periodically, every six months
You'll need to open case and remove all dust from it and from vents. You'll need to be very care full while cleaning inside case. You can use vacuum cleaner but be sure motor is far from computer and it's components. Also, you should earth yourself by touching any metal object that you know it's earthed, like a radiator.