FallisPhoto has quite good tips for any DSLR users on how to clean lenses.
He explained that we must use blower and lens brush first to remove as much grit as possible then we need some commonly used solvents in camera restoration and lens cleaning which are:
1. denatured alcohol, used to remove tar (from cigarettes, or pine pollen) and detriorated light seal material (sometimes found stuck to rear lens elements). Do NOT use rubbing alcohol; it will work, but it is not a benign solvent and it can attack some balsam cements used to glue lens elements together.
2. naphtha (Ronsonol lighter fluid), used to remove grease and oils (naphtha is REALLY good for fingerprints).
3. distilled water, used to remove everything else.
These are all benign and won’t harm your camera if you just keep them out of the electronics.
4. a 50/50 mix of hydrogen peroxide and ammonia, used to remove lens fungus.
You can read the complete tutorial here