Validate JWTs in this order:
Parse and decode the three parts
Verify signature using the correct algorithm and key
Check expiration (exp claim vs current time)
Validate issuer (iss claim matches expected)
Validate audience (aud claim includes your service)
Never skip signature verification. The "none" algorithm attack tricks servers into accepting unsigned tokens. Always verify against a whitelist of allowed algorithms. Use established JWT libraries rather than parsing manually.