This is what Apple says about cleaning
"Cleaning iPhone
To clean iPhone, unplug all cables and turn off iPhone (press and hold the Sleep/ Wake button, then slide the onscreen slider). Then use a soft, slightly damp, lint-free cloth. Avoid getting moisture in openings. _Don’t use window cleaners, household cleaners, aerosol sprays, solvents, alcohol, ammonia, or abrasives to clean iPhone._ If your iPhone has an oleophobic coating on the screen (iPhone 3GS only), simply wipe your iPhone’s screen with a soft, lint-free cloth to remove oil left by your hands and face."
You will have to make your own decision on how and what