Rule of Thirds
Use the grid option on your smartphone. You want the main subject of your photo to be centered at the intersections of the rule of thirds grid- not smack in the center of the photo!
Beware of Backlight
The human eye is drawn to light- so you want the light in a photo to be in front of the subject, not lighting the subject from behind.
What’s physically behind the photo can make or break an otherwise perfectly lit, rule-of-thirds abiding photos.