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.
Use speed when capturing your pictures. If you take too long, the subject could move, the sun could move behind a cloud or it could start raining. Anything could happen, so don't delay. A camera which allows you to make quick photos will give you the best results.
Take successive photos of your subject if there is a chance that it might move. Certain subjects, such as wild animals, won't just wait patiently for you to take your photo. In this case, take one shot quickly so that you have something to work with. Then, if the subject hasn't moved, take more shots with better positioning and composition.