The major problem with this type of program is the reward must be something that your sales staff really wants. If the reward is something that is not needed or will cost money if they win, the program will not be successful. An example of a reward that costs money if you win would be a trip. On any type of trip there are always side expenses and tips that have to be paid. There is also the loss of sales when you are on the trip.
Gift certificates are the same thing.
A lot of times a little gift for buying right now will really improve your overall sales performance. Or a gift for letting me show you our product can really open the door. Here the secret to success is to be able to offer what the person really wants and has a high perceived value. If you use calculators or alarm clocks or maybe golf balls as your incentive item you will only attract the people who want or need these items. That usually is about 3 out of a 100.