Never use the same password for multiple accounts.
Use complex passwords or passphrases.
Use false answers for security questions. For example, if they ask what was your mother's maiden name, use a false answer like T1000. Basically something that can't be dug up through social engineering or a good background check.
Enable two factor authentication. In the order of most secure, use a two factor authentication app like Google or Microsoft Authenticator. Next use an email address with 2FA enabled. Alternatively, you could use a Google Voice and then enable 2FA on that Google Account.