All you need to do is make sure your 3DS is on and in sleep mode. Just walk around where there's plenty of people. You have a better chance of street passing someone if you do. The light on the top right corner of your 3DS will start blinking green if you pass someone.
You have a chance of getting a message via BuzzNav saying you have a new Mirage spot to explore, or even a gift for you in a Pokemon Center (which should be the Eon Ticket)