1. In a quiet cinema before the movie starts
You'll have to whisper loud enough when it's really quiet.
2. In a lift, where it's just you and one or more innocent strangers
The point is to remain stealth-like. The person(s) cannot know where the whisper came from. Don't move your body.
3. At a fast food drive-thru, when they ask for your order
You could either 1) drive away after that and 2) Say 'Y U NO HAVE YUSUF TAIYOOB?' after they claim to not have any dates.
4. In a lecture hall when everyone is avoiding the teacher's question
This is the perfect time for you to rise in popularity in your class. Don't let it go.
5. In the middle of a phone conversation, when you suddenly stop talking and the person says "... Hello? You there?"
You must not give in when there's silence in the conversation. Wait for the person to say "Hello?" twice, and go for it.
6. When you lean over to your GF and say, "Babe, one more thing..."
Do this in the car. Park at the side of the road (where it's safe). Make her expect something really bad, or really good.
7. When you're in the toilet and someone is 'minding their own business' in the next cubicle
8. At 12.30pm, when your colleague asks, "What do you want for lunch?"