How do I check an Awazon address is genuine?
Copy it from a signed source, then compare it against the address the login captcha prints. They must match.
Short answer. Two checks. Verify the PGP-signed mirror list once, and every session compare the address in your bar against the one the login captcha prints. Match means genuine.
The signed list
Awazon publishes its addresses with a PGP signature. Verifying it proves the list came from the market and was not edited. Import the market key once and check the list against it. See how to verify a PGP-signed list.
The captcha check
The genuine login prints the market's own address into the captcha. Hold it against your address bar. A clone cannot easily serve the correct address in the captcha while sending you to the wrong one, so a mismatch gives it away. Run this every session, because a bookmark can go stale.