On this specific picture one thing happened to you.

You are crouched next to two standing people. That has no sense. It was probably because you wanted to be "too" inventive, because you are too worried of doing something cool.

Interacting group

Depending on how really close the group are (and I do not mean spacing) the interactions reflect that. Probably it is also a cultural thing. Some cultures are less "expressive" than others.

Let us take a look at some stock images: https://www.google.com/search?q=happy+group+photo The basic idea is that people interacts. In almost none of thoose random images no person try to stand out. The full group include someone else.

If you want to be more expressive (different than cool) simply hug the persons arround and do not be afraid of smiling.

What you can learn

When directing people to protrait photos, one technique to smile is to do it but do not close your lips. Breath trhu the mouth. That opens a bit the mouth and gives a more natural look.

Another tip when directing people if for some reason you can not hug all the people arround you while standing, is do something with your arms. Cross them, take them to your belt, etc.

Do not worry too much

I do not see wrong that you learn this kind of posing tips. If this is part of learning things that make feel us more comfortable it is great.

But never fake things. Be yourself.

As this is a photography forum

If you are the one on the other side of the camera, please include the feet of the persons in the front row!