After countless embarrassing Self Portraits, I wanted to venture into photography people. So at first I asked a few friends to be test subjects and after many failed attempts and hundreds of useless photos later, we got a few keepers and called it a success haha. After my third of fourth shoot I started getting comfortable enough to experiment with lighting, posing, composition and different locations. All I can say is trial and error and don't be afraid to step out of your comfort zone. We learn more from trying new things and making mistakes than simply doing the same thing over and over that we're comfortable with. So don't be afraid to fail.
I ended up landing into doing Senior Portraits for quite a few years. I do them randomly here and there but not so much anymore. But it was definitely a huge learning experience and helped me eventually shoot weddings. Posing brides, communicating with clients, how light/shadows affect the body, etc.
So as I've been preaching in these posts. Practice and practice some more and don't be afraid to try something different, even if you "fail". Learn from your mistakes and keep fine tuning.
Enjoy some portraits :)