It must satisfy four basic elements to be effective:
1. Irony. It must be in some way ironic and emotionally involving - a dramatic situation that is like an itch you have to scratch.
2. A compelling mental picture. It must bloom in your mind when you hear it. A whole movie must be implied, often including a time frame.
3. Audience and cost. It must demarcate the tone, the target audience, and the sense of cost, so buyers will know if it can make a profit.
4. A killer title. The one-two punch of a good logline must include a great title, one that "says what it is" and does so in a clever way.
