The other day I was out with a friend, and they needed to grab a picture of a document with their iPhone. I watched painfully as they would position the iPhone just right, touch the screen to focus on the document, wait for it to focus, and THEN hit the picture button. The problem was simple – the action of hitting the button would cause the camera to get slightly out of focus.
The solution was simple, but others may overlook this tip. When focusing up close, such as when grabbing a document, touch the screen to focus and immediately afterwards hit the shutter button. Once the camera finishes auto-focusing it will go ahead and snap the picture, leaving you with a perfectly clean picture. The good news is that no careful hand balancing is required, and it is much faster than the alternative. Naturally, if you try this in a situation where the camera simply cannot focus, such as being too close to the subject, you are still going to get a blurry picture.