One of the challenges with many camera phones is keeping them maintained and clean.
Phones spend a lot of time in pockets, in bags and being used in all manner of weather and conditions. As a result they get dirty and can easily become damaged - fingerprints are a common problem on camera lenses - especially if your phone doesn’t have a lens cover.
From time to time clean the lens of your camera using a soft cloth (sunglasses cleaning cloths are great).
Read more: http://digital-photography-school.com/how-to-use-a-camera-phone#ixzz0NP1MlyN8
Source: http://digital-photography-school.com/how-to-use-a-camera-phone