Click a button and press a key to rebind
Configure what action each mouse button performs
Don't upload forbbiden custom skins, especially if it's someone's face, you might get your skin banned or yourself banned from the game.
Don't use other people's nicknames in chat or as your name in a derogatory way, you might get muted or banned from the game.
If you cannot connect to the servers, check if you have some antivirus or firewall blocking the connection.