- Limited time frame for an offer (buy until 23:59 today!);
- Limited quantity (only 3 left);
- Pick your audience (we only sell to …);
- Unique product (only us, in the whole universe …);
- Exquisite conditions to get an item (you have to do something, you have to pay a price, you have to put yourself on a waiting list);
Scarcity sells; just have a look at collectible luxury items – you can only buy them for a certain time frame, they are in limited quantity, they are very expensive; lots of conditions to get an item.
Apple sells expensive and unique products (only they …).
Note: Also see the Yahoo! Group on which I present similar issues: IMRo. To join, email email@example.com and reply to the confirmation email.