I've been in wireless for 7+ years, so here are my recommendations. Rubbing alcohol is the best to use on most of your phone (buttons, speaker area, etc) for getting rid of germs and oils, however on some older models that have the plastic encasement over the display you will want to use glass cleaner on that particular part or else the plastic covering may turn opaque.

I know you didn't specifically ask for this, but you may also want to occassionally clean the bottom where you connect the charger. For this, you can dip a soft bristled toothbrush in a bit of rubbing alcohol (do not immerse it) and gently brush the connection area to free up any goo or small particles that are wedged or blocking your connectors.

Another note: Never use any type of liquid behind the battery. Most phone manufacturers have a dot or line on the back behind the battery that - if gotten even remotely wet or damp - will leave a tell-tale mark. It won't hurt your phone, but if you should have an issue while it is under warranty they will assume it is water damage and won't even bother taking it apart to see otherwise.

1. Remove the external parts. First off, you should remove the external parts of your cell phone like the cover and the keypad. And then you can clean every part easily. In some models, the keypad can't be removed easily; don't remove it in this case. I mean the easily removed parts.
2. Use rubbing alcohol. The second step is to use rubbing alcohol; it is the most effective cleaning agent you can use to clean your cell phone parts. You can add a little amount of rubbing alcohol on a small part of a clean cloth or a clean piece of cotton.
3. Clean the buttons. You can use this small part of cloth to clean the buttons of your cell phone. The part of cloth imbued with rubbing alcohol will remove any small particles, oils, dust, etc. You will discover the great difference after you finish the cleaning process.
4. Clean your cell phone's screen. Now you want to clean the display screen. This part is different from the other parts of your cell phone, so I suggest you use a glass cleaner to clean this part. Don't use the rubbing alcohol to clean it; use a clean part of cloth for this.
5. Clean the cover of the cell phone. The cover of your cell phone can be cleaned easily using the rubbing alcohol, as I mentioned above, you should use a little amount of rubbing alcohol on a small part of cloth to clean it. If the cover of your cell phone can't be removed, don't try to remove it, but rather simply clean it externally.
6. Clean the speaker area and the connectors. The speaker area can be also cleaned using the rubbing alcohol. There are other important parts to be cleaned also -- the connectors at the bottom of your cell phone. By connectors, I mean the place where the charger connects, the headphone connects, etc. You could use an unused toothbrush with a little amount of rubbing alcohol, and then start to clean the connectors to remove any dusts and small particles from these parts.