Recommended and mentioned products
Bitwarden is a free and open source password management solution for individuals, teams, and business organizations.
freemium $10.0 / Annually (Premium)
I would recommend using a password manager to auto-generate and store your passwords. You can use something like bitwarden, https://bitwarden.com/, which is open source. And if you'd prefer not to store anything in the cloud, most computers have keychain managers that will generate and store passwords as well. On mac, lookup 'keychain access,' it comes pre-installed.
Secure your life, forget your passwords
Have a look at MasterPassword. You don't need to remember a site's password with it. You can write down, (in abbreviated form) the constituents for generating a password.
Download Password Generator for free. Pwgen is a small, GPL'ed password generator which creates passwords which can be easily memorized by a human.
If you want to generate them locally instead, you have PWGen for Windows or any of its open source alternatives.