The main rule is simple: never click links from emails and messages, even if they look official. Always open bank websites, social networks, and important services manually by typing in the address bar or using bookmarks. Phishers are really good at faking emails, and the link can lead to a copy of the site that looks like the real thing, but it's still a trap.
Second important thing - pay close attention to email addresses and URLs. If an email supposedly from Sberbank comes from an address like sberbankk@mail.ru or sber-bank.info, it's fake. Real companies write from official domains. Same goes for links in emails: hover your mouse over them, see where they actually lead before you click.
Use two-factor authentication everywhere it's available - in email, your bank, social networks. Change your passwords regularly, especially on important accounts, and make them complex: letters, numbers, special characters. Keep your browser and operating system up to date, and it's a good idea to install decent antivirus software on your PC. And basic rule: never enter your data on sites with http (without the S), only https, where the connection is encrypted.