First important rule as a player: shower.

So essentially it's all about respect and communication.

he didnt mention that "what happens in game, stays in game". its the hardest one i think. for someone to look at another player and insult them in game, and not translate that into real life

There are three things I hate most at the table:
1. Phones
2. Phones
3. Phones

My first group at college had a bit while everyone got used to the game and each other. After that, I offered them 4 possible missions. Very quickly, they realized each mission focused on one of their characters. They began referring to them as "your mission". And what happened was they began to defer to current "star" for the direction. One guy asked what he should, probably concerned he was about to make a crazy decision and that the others won't go along with him. The others told him to do whatever he wanted; it was his story. And then there were other missions where no one was the star, but I liked giving them each a small mini-campaign. And I liked how the players respected that.

"Hello! I am Matthew Mercer..." gives me so much peace and hope during this quarantine

kicking out a player is easily the hardest thing to do in DnD, or any tabletop

In my weekly game in college (that I participated in, not GM'd), I really liked something we did at the end of every game. Everyone would vote for the best character moments of the night. The person voted for would get bonus XP. Only like 100 or so, it was mainly symbolic. But it was a great way to recap the night, and get a feel for what this group of players enjoyed.
It was also fun the variety of things that won. Sometimes you won on pure role playing. Through superior acting or a great one-liner or something. Other times you might just win because a dice roll allowed you to do something unbelievable, but otherwise didn't have anything to do with you.
It was fun :)

Played this for my players, 8 & 10 year old daughters. "Be respectful, that means give me the Robe of the Magi, right dad?"

and if stuff gets heated, do not be afraid to call it a day early.

My group had this one jerk who had no manners. He never paid attention when it wasn't his turn, he straight up brought a Nintendo Switch to the table. His character finally died and he got so mad he actually quit D&D

I end  every session with a few questions;
1) What can I do to tell a better story?
2) What can I do to run a better game?
3) What would you, as players, like to see?
4) What would your characters like to see?

Matt: Be respectful and appreciative of your game master
Our group, who practically worships him: Way ahead of you

I feel like this is just "How to interact with other humans" ans it could be just resumed to "Don't be a jerk" x)

He starts off by saying, "Welcome to my silly video series..." But I don't find these videos silly at all. They're super helpful, informative, and should be a must-watch for any tabletop group. I think "lighthearted" or "casual" is a better choice of word. :) I hope he does one on meta-ing. That's my biggest pet peeve.

The playgroup I am currently most frequent with sat down and we had a really mature and open conversation about the things that are and are not working, and the next session had a noticeably better flow and I think everyone enjoyed it more. I was really glad we talked about it, especially since I was part of the problem, and my part was escalated by some miscommunication. We managed to clear it all up like the adults we are. It was a great feeling.

Don't be the guy who just say " i don't care about the necromancer trying to conquer the world, i'll just stay  in the city, the rest of the party can go if they want to", or leaves the party or  dodges plot hooks or makes the entire campaign impossible to resolve.Regardless of the legimitate roleplaying justifications your character has , you are there to play with the other people, using(at least a big share) of the material your DM has prepared.Some DM like to run open, sandboxy campaigns where this behaviour would be partially tolerated, just be aware of how much DM-written content you are dodging and how much your story can fit into the party's story.

i found that, atleast as a player, it's much easier to roleplay when there is less people at the table. I have noticed that it's easier for the DM to listen to everybody, and that it doesn't take as long waiting for your turn, and it also makes it easier to manage your party.

There is a technique that might be helpful: When as a GM I have to create a BUNCH of story elements, like when I have to come up with a dozen NPCs or something like that on the fly, I use the creativiy of my players. I tell them to come up with an NPC concept each, and voilá, I already have as many NPCs as players. It can be very helpful to use the creativity of a whole party to do the job instead of just one slow brain.

One thing I cannot stand as a GM: When players don't pay attention. It's a very rare case, since most people do their best to remain attentive, but occasionally I get the asshole who's texting while doing D&D or just simply not caring and doing a little as possible. Here's a little tip on making it work:

Be sure to address them and let them know what they're doing is bothering you and disrupting the campaign. Usually, one warning is enough and they respect it and get along just fine. If this is repetitive, then I suggest drastic measures and booting them from the game, seeing as they care little or not at all about what's happening.