How do you cry for film?

If you have seen the film before and know what bits are sad then, about 5 - 10 minutes before this scene, stare without blinking. Keep staring even if it hurts and then when the sad bit comes up, blink. The tears will fall and it is really satisfying! I am the champion of staring contests and once i didnt blink for 15 minutes! So take this advice because it looks really realistic.