I’m just a straight male. Are my pronouns he/him?

If you want them to be.

Is that how I should tell people? Do you actually tell them as you meet them ? Do I have to wait for a certain social cue ?

A decent social cue to use would be if someone has mistakenly used one of the 'default' pronouns (he/him or she/her). Just be polite and understanding about it.

And about respecting other people’s pronouns. How do i figure them out ? Is it a big faux pas if I don’t before I know them ? Is it a faux pas if I refer to someone I just met and I assumed to be male as he/him?

You don't know what you don't know. The only people who would give you shit before you could have reasonably known would be, frankly, someone looking for drama/a fight. Treat those people accordingly.

I’ve never seen anyone referring to anyone irl by non conventional pronouns. Is it an actual thing or is it currently being pushed to make the world a more inclusive place?

It is worth keeping in mind that we are talking about a relatively small crowd of people that identify as non-binary or use non-standard pronouns. It is pushed mainly because it prevents exclusion for these people and honestly it costs nothing anyway.

It's also handy for the trans crowd, as although they may use standard pronouns, they might not be the ones they currently appear as.