What are the most effective ways to prevent a ransomware infection?

Backups above all — plus current AV/firewall, patched software, email caution, and disabling Office macros.

The prevention checklist:

• Backup, backup, backup — and disconnect/relocate the backup medium afterwards (so it survives both ransomware and a fire)
• Up-to-date antivirus and an active firewall
• A patched system and apps (browser, PDF reader, Java, etc.)
• Careful email handling (spam/phishing awareness)
• Disable automatic execution of Office macros (a classic infection vector)
• Heed User Account Control (UAC) prompts

Why backups top the list: they're the only measure that guarantees recovery after a successful attack. Prevention can fail; a clean, offline backup means you can rebuild without paying.

Tip: Macro-disabling is high-value and low-cost — booby-trapped Office documents remain one of the most common ransomware delivery methods.