Username and password logins are commonly used to secure access to systems. The username is a public identifier, and the password is a secret known only to the user.
Password recommendations
The most important part of a password is that it is not guessable. Don't use your birthday or another known piece of information.
Another is the length and variety of characters used. This helps prevent brute force attacks.
Do not use the same password for multiple sites. If it is compromised, you will have big problems.
Password management
Because each site should have a unique, hard to guess password with a variety of characters, they become hard to remember. Password managers securely store username and passwords for sites and have a UI allowing you to quickly access them.
Convenience is a big factor, there are some good options that will work on your device and operating system without frustrations.
These systems also need to be trusted and secure. Check reviews on tech sites for any negative information about the company.
Storing passwords
Never ever store or transmit passwords in plain text.
When a user sets their password, it's hashed value is stored. That means that if the database is compromised, the passwords are not easily read. If you find the hash method and salt key, you can try to guess the password and compare the hash, but you can't get password directly from the hash.