Look at this recent photo of Penn Jillette and a fan:

Now, you need top know that Mr Jillette is a big guy. Very big. Very tall, in particular. And his fan is not all that tall. So the height difference is enormous.

And hence, I did what I often do: I tilt a little. When I shot, but also in “post”:

As you can see, the difference is more pronounced in the original. Without making it ridiculous, you can manage to reduce such height differences by using this simple technique. While shooting or in “post”: tilt a little. Keep strong verticals out of the image if you can, tilt, and Bob’s your uncle.