Long passwords are better. The most secure passwords will be somewhere between 10 - 20 characters long.
Don’t use common words or phrases like a movie quote, favorite saying or family names.
Test your password to ensure it is secure. https://howsecureismypassword.net/
Use different passwords for all of your accounts (work, personal email, banking). If someone were to gain access to your personal email they won’t be able to use the same password to access your bank account.
Don’t write your password down on a post-it note or next to your computer. Instead use a password manager like lastpass, dashlane or 1password. These will create and store all of your passwords for you.