Ask HN: How do you keep your PC safe?

I could explain to you SQL injection or a rainbow table, but in practice, I don't know how to keep my own PC safe (eg. when browsing on public WiFi). What configuration do you use to keep your computer secure? 1. What antivirus do you use? 2. Do you use a VPN? A personal one or a service? 3. What Firefox/Chrome plugins do you use? (eg. HTTPS Everywhere) 4. Do you use a program to store passwords? 5. What do you use for backups? 6. What other tricks do you have?