The thing is that if you act suspiciously, you will get caught. So. Rule no.1. Don't be greedy, just shoot what you can at where you are. Hide your equipment. Don't even look. Don't aim, "use your instincts".
Think before you act. Go and observe, without a camera for a few times, so you can think of a strategy. The most important thing is that you don't get caught, second important thing is the pictures you took.
Besides, Pedro is my idol, I've always liked his work. His posts are the reason why I registered here. He knows what he is doing.