Take your pictures quickly. The longer you hesitate, the better the chance that your subject will move away, break their pose, or become tired and stop smiling. Start taking shots as quickly as you can, and don't worry about getting the camera perfect before the first shot. The faster you shoot and the more photos you take, the better your chances are of getting a good one.
Is photographic memory real? Read More: Are photographic memories real — and could you have one?