Day and Night
You must cleanse your face every night and every morning. The morning clean removes surface oil and dead skin cells accumulated during sleep.
Be gentle
Remember, it needn't be anything more than a quick wipe with a damp face cloth. Too much rubbing, washing and cleansing is counterproductive and can cause more problems than it solves.
Deep cleansing
The night time cleanse, on the other hand, should be considerably more thorough. You need to fully remove all the impurities that has built up during the day, as well as removing all traces of make up before you go to bed. Your skin repairs itself while you sleep. Any residue on your face hinders this process and leads to a whole host of skin problems. So, never go to bed with make up on!