For the most beginner of beginners - I would say that the best advice is to control the center of the board, play aggressively / make an attacking move whenever possible, and DON'T be afraid to trade pieces.
If you don't have a move that attacks your opponent and forces them to play defense, develop your least active piece.
Also, learn the King's Indian opening. You can use it as black or white, and it's one of the easiest openings. I also think it's a good opening against beginners, because they make a lot of mistakes against this. So, 1) you'll be able to beat beginners - and winning is always more fun than losing; and 2) you'll learn to watch for your opponents to make mistakes - and that will help you learn to avoid making common mistakes.
These two videos got me from ~700 to ~1000 in about a week. And they got me to the point where Chess was actually fun instead of a being a frustrating minefield I tried to navigate until I inevitably made a blunder and self-imploded.
If you don't have a move that attacks your opponent and forces them to play defense, develop your least active piece.
Also, learn the King's Indian opening. You can use it as black or white, and it's one of the easiest openings. I also think it's a good opening against beginners, because they make a lot of mistakes against this. So, 1) you'll be able to beat beginners - and winning is always more fun than losing; and 2) you'll learn to watch for your opponents to make mistakes - and that will help you learn to avoid making common mistakes.
[1] Controlling the center of the board and making attacking moves - https://www.youtube.com/watch?v=g5jTMqdYXWM&t=1100s
[2] King's Indian opening - https://www.youtube.com/watch?v=kK0cq6UBt1Y
These two videos got me from ~700 to ~1000 in about a week. And they got me to the point where Chess was actually fun instead of a being a frustrating minefield I tried to navigate until I inevitably made a blunder and self-imploded.