The value of an iPhone, iPod, iPad is not only measured on its price tag but also on the amount of care you give it. Throughout this article I'll refer to the iPhone, but the same information applies to the iPod and iPad as well. Since the iPhone is a much used device in your day to day living, it's gets subjected to lots of different environments, some dirtier than others. To get longer life out of your iPhone and maintain it's condition you must keep it clean.

You don't actually need to be an expert or buy intricate gadgets or chemicals to clean your iPhone. You just need to be careful.

Before we get started we're going to need these things:
 

Your iPhone (of course)
Microfiber or other similar lint-free cloth (usually one comes with the iPhone)
Old or New (very) soft (and dry) tooth brush
Cool water
Safe and quiet spot/area (for the cleaning)
 

Follow these steps:
 

All cables must be disconnected. Don't ever start while the iPhone is attached to a computer or any other device.

Turn it off. This can be done by depressing the "sleep/wake" button at the top of the device. In about 3 to 4 seconds a red slider will appear on the screen. Drag the red slider across the screen with your finger. If you are having difficulty with this procedure, refer to your instruction manual.

Moisten (not soak!) the corner of the soft microfiber cloth. It is preferable to use distilled water because it carries less impurities.(Never apply water or cleaning solutions directly to your iPhone)

Gently wipe the iPhone (with the dampen corner of the cloth). Pay special attention to the touch screen and avoid wiping the ports. Wiping should be in an up-and-down motion. Do not wipe in circles because this can leave smudges behind that are unsightly when you turn on your iPhone.

Use the dry portion of the cloth to remove any moisture that remains on your phone. Do this gently until you are satisfied with the cleaning results.

Use a very soft tooth brush to clean out the speaker and microphone cavities. There are two speaker and microphone cavities at the bottom of the iPhone and one at the top, which usually collect lots of dust and grime. These need to be gently cleaned with the very soft (dry) tooth brush. Don't use a lot of pressure, as you don't want to damage the dust shields.

Turn it on. When your iPhone is completely dry, it's ready to switch on again. You can power it on by depressing the "sleep/wake" button. The "Apple" logo should then appear on the screen.
 

Congratulations! We're done.

Try to do this regularly to keep your iPhone looking at and performing at its best.

And to wrap it all up, let me give you some significant tips and cautions:
 

You should purchase a case to house your iPhone in to reduce the amount of surface dirt that may come in contact with your iPhone. The housing also prevents oils from touches of your fingers which could leave prints on your iPhone. At the very least a clear touch screen protector, they are very cheap and available in most shopping centers and on eBay.

Avoid cleaning your iPhone with liquid or aerosol cleansers containing alcohol, ammonia or other abrasive ingredients. These regular household and window cleaners can harm the touch screen.

Be careful not to immerse your iPhone into water or use it in extremely wet places, such as the swimming pool. Moisture may cause damage the inner structure of the iPhone. You will need to take your device to an iPhone repairs specialist if it is exposed to water.