Polish It Up
Cleaning your touchscreen smartphone is kind of like cleaning your LCD monitor — you don't want to use any harsh chemicals, or even more damaging — water. Using a tried-and-tested cleaner like iKlear ($21) will ensure you won't damage your phone's sensitive bits. Use the included microfiber cloth (or one of your own), and shine that baby up.
If you don't want to spring for a special formula, a 40/60 alcohol to water mixture on solid phone parts and keyboards should be OK for your devices (use a damp cloth and/or cotton swab for small and hard to reach places), however you do not want to use any sort of alcohol, ammonia, or harsh cleaning agent on touchscreens.