Light and Shadow, along with perspective will give you a "real" look. Most folks do not look at the WHOLE picture...only the subject.
Look at the trees growing through people in many snapshots.....DOES IT LOOK REAL ? if not WHY ?....Take your time and think!!
Example...this looks like a model....
While this one makes you look further.....
and as Marcos said shoot from many angles....(you can also hide flaws this way!)
Different angles make for unique looks....
Like one of my favorite shots of my '34....