Cleaning White MacBook
In my (too many) years of experience, the best "mix" you can make is composed of:

Seven parts of water (distilled if possible but in the case of the plastic it won't make much difference)

Three parts of alcohol (the same used in medicine, sold in pharmacies). 

So you actually put seven "somethings" of water and then three of alcohol. Mix, and store in a bottle, closed (or the alcohol will evaporate!). It can last for months. Use soft cloth to clean everything, even screens. Don't use toilet paper on screens. 

note: Somethings can be, glasses, spoons, lid, etc. The important thing is that you use it for both water and alcohol, so it's the same proportion.