Easy to do on Contract 3. You will start the mission next to a house in the top left corner, which a detective will come by and examine every few seconds.
Just go in the front door of the house to "hide," wait until the detective comes by, and pop out. He will notice you and his flashlight will turn red, then just hit
to hide again. Wait until he resets and has "lost" you, pop out again. Rinse and repeat.