The answer is landscape
As you may have noticed on my YouTube channel (please subscribe), I’ve started filming more content. Mostly just little vlog-type content on my phone.

I do it because I like videos, and it’s been fun, also as a learning exercise. And one of the most crucial things I learned, I see has not been adopted by others. So I’m going to help you learn an easy but crucial lesson about filming video on your smartphone. How to hold your phone correctly. The answer is: landscape, as in length-wise.

This easy-to-follow diagram will help illustrate.
Nuff said.