Wheel Rotating Tip
Probably the best way to rotate the picker wheels is to do the following. Looking at the leftmost wheel, while holding your hand in somewhat of a perpendicular angle to the wheel, place your forefinger over the 1 and slide upwards. You can actually slide all the way to the top edge of your iPhone and the wheel will continue rotating. The big advantage of this method is that you will not obstruct your view. Many user's do not realize that you can slide as far as I just described and still be affecting wheel change.
Many user's (myself included) first did this by keeping my hand nearly parallel to the wheel when rotating. You will rotate the wheel, but you will also block your view. That is not what you want to do.