What makes a password strong
Length matters most. Each extra character multiplies the number of possible passwords, so a random 16-character password with mixed characters would take longer than the age of the universe to guess by brute force. Avoid words, names, dates and keyboard patterns, which attackers try first.
Good password habits
Use a different password for every account, so one leak can't unlock the rest. Store them in a password manager, and turn on two-step verification wherever it's offered, especially for email, banking and social media. The National Cyber Security Centre also suggests three random words as a memorable alternative for passwords you need to type often.