Step 1: Master the Scream
Hold it in for as long as you can. Aim for 30 seconds or more. Practice in front of a mirror to ensure a good scream face.
Step 2: Develop a Good Story
You can't just scream for no reason. You need a valid excuse. Practice your story telling skills, and be prepared to explain why you're crying in public.
Step 3: Choose Your Setting Wisely
Not all public places are created equal. Opt for a crowded area where no one will notice your tears, like a grocery store or a crowded elevator.