Getting the right focus
Tap on the subject to focus, alternatively tap and hold anywhere on the screen and move the slider up or down to adjust exposure.
Using ProRAW for better editing
If you like being creative and play around with editing, do try the Apple ProRAW mode. The additional information that it provides in shadows and highlights will give you an edge that you require for post production.
How to make the most of
Portrait Mode is fantastic and it gives you a very realistic bokeh to make your photographs stand out. Do use it whenever you are taking pictures of friends and family or you want that beautiful blur while taking photographs of flowers. Portrait mode lets you choose f-stop before and after you have taken a shot (F-stop decides how much blur you want in the background).
Use the grid
Use the grid option, it helps you compose your photographs better. Also, iPhone does allow you to shoot in 16:9 ratio for wider shots.
Using Live Photos can make images better
Use the Live Photo option. You can take one photo and chose the best frame afterwards. Specially useful when taking pictures of a large group. Also use Live photo option for long exposure shots. The light trails and water falls look exceptional in this mode. All you have to do is take a Live Photo and swipe it up to see the effects that you can create.
Last but not the least, do clean the lens often, you can use micro fiber to wipe the lens gently.