iPhone having a good quality of camera, but there are some tricks to improve the quality of your pictures, you have to make yourself 100% stable. This will not be possible when you use your hands for pressing the shutter button on your phone. To achieve maximum stability, you have to click photos without using your hands. Yes, this is possible. You can take photos using your headphone. When you are ready to shoot, simply press the center of the headphone and done!
Try this and judge the quality of pics you captured after trying this...