Best thing I found is a MonsterCloth from Amazon. They work great at quickly cleaning prints, smears and smudges from the screen of tablets, touch phones and PC screens. You can get them at a good price and you can probably find the product at places like Office Max etc under a different name.
On all my devices I use a fairly large micro fiber cloth. It rarely requires any liquid and does a great job very quickly. You can get them in bulk very inexpensively from Amazon. I keep a small one in my vehicle and one large one in my office.