I have a few questions on how to best behave to be as welcoming and inclusive as possible without sounding bad. I hope you guys don't hate me.
I'm just a straight male. Are my pronouns he/him? 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 ?
How about online. Should I tell people or have it on my personal profile somewhere?
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?
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?
I'd love some help with all of this.
Many other answers emphasizing to be on the considerate side are good. I just want to add two things.
Some folks have said that when the way you present matches your pronouns, you have less need to offer them. Personally, I think it is good to offer them anyways when meeting new people. People don't always present exactly in a way that you might expect their pronouns to indicate. As one example among many, someone may present very femme but prefer they/them pronouns.
This also helps us (you and me both!) unlearn some of our learned gender associations and habits of inferring gender based on appearances. It can sometimes be unpleasant to deal with someone that's clearly trying to figure out their gender identity visually or by voice, etc - trans or not. For an extreme example, there are even cis people getting harassed about which bathroom they're using (the one aligning with their gender) based on reactionary assumptions.
Finishing up that topic, offering your own pronouns is also a way of letting others know it's okay to be more open around you, that you are a bit safer than the average person. This can be most impactful, imo, for people who are trans or questioning but who aren't out yet. A lot of folks are struggling at that point in their lives and it can really help to know who is safer.
My final thought is that when you don't know someone's identity, it's good to get in the habit of using their name or they/them. If it's a real person irl, then you'd still want to ask for pronouns soon-ish. Occasionally, they/them-ing someone can also become unpleasant, though usually it'll be obvious from context (e.g. someone who is trans and strongly prefers he/him might perceive continued they/them to be a form of harassing them). Grabbing pronouns soon-ish avoids any awkwardness.