As Governors Island opens this weekend for its 13th annual public season—and is open 7 days a week—until September, here is a list of things to remember before getting in line for the ferry. 1. Before leaving home, charge your mobile phones to 100 percent. The island only got electricity in 1905, and getting a charge is like finding the ghost of U.S. Grant. 2. Bring cash. The bank closed in 1996. The pop-up shops and food vendors appreciate your cash. 3. Wear comfortable shoes. Unless you are going to walk off the ferry and sit down immediately, you’ll probably walk at least one to three miles (or more) in…