The multi-touch glass screen is the single most important part of your iPad. Unlike most device displays, you not only view the interface through it, the screen is the interface. Even with the fingerprint-resistant oleophobic coating, the iPad screen will get dirty quickly and easily.
To clean your iPad screen, never use any type of cleaning solvent such as Windex or similar chemical products. Use only water.
Ideally, use water with a lint free scratch resistant cloth (microfiber is best) to clean your iPad screen by dampening the cloth slightly. Then clean the screen using soft, even strokes.
The 3M Microfiber Cleaning Cloth is highly recommended.