No Power

Clean the heck out of the battery clamps with a legit battery post cleaner.

If you still get nothing, use a meter or test lamp and check for power at the starter relay stud to ground. If you get power there, but still have no lights, etc, feel the fuse link which runs from that stud into the bulkhead connector. You can probe the front of the connector. If you have power at the firewall side of the connector, most likely the problem is right in the connector itself