Secure yur router - secure your home!
Check if you not still have your default pw's on your devices ....
And a good password has numbers, letters and special characters. It should be at least 8 characters long and never use the same for different accounts.
To manage your usernames and passwords you can use a software ( Passwordmanagers ) to manage your different passwords on a save way. Make backups from the Software' s file.
Simple but effective!