How to offer online coupons?

[Tony]

Without someone abusing it by giving it to their friends? Eg, an exclusive coupon for a select class of members form a website.

[Yasir]

You can apply the restriction to use for your registered members or subscribers only. Or you can apply some other conditions such as member is already following you on "facebook" or "twitter" etc.

Or member has already purchased your products or services at-least once in past.

[mtlguy]

have a unique serial code on each coupon that will be generated when the requirements are met (user signs up, gives information, requests coupon etc)

then once the coupon is redeemed the serial will be deactivated