How Do I Use Them?

It depends on the type of coupon.

The most common two are special links to hidden pages on the retailer's website (Amazon.com tends to use these), or a special code to be entered in the "Gift Certificate" or "Coupon" space upon checkout (such as the codes offered by Reel.com and DvdExpress.com).

In either case, simply click on the coupon that appears in the list, and start shopping. 

If the coupon is a special link, then that page will explain what you then need to do (generally, nothing; a 'cookie' will be set on your PC, and the discount will be applied -- and appear -- automatically when you check out).

If, on the other hand, the coupon is a code, you will be taken to the home page of the retailer's site, and a small browser window will be opened at the upper-left corner of your screen.  This window will show the code; either keep the window around, or write the code down someplace before you close it.  Then do your shopping in the main window as you normally would.  When you check out, there will be a space to enter this code, generally around the same screen where you enter your credit card information (although sometimes it's the screen afterwards).  Look for a space called either "Gift Certificate" or "Coupon."

After you've entered the code, and before your order reaches the final submission, there will always be another screen showing the updated total.  You will always be able to see the results of the coupon before you reach the final submit screen.  If the coupon is rejected, you will be offered an opportunity to use another code.

What are the restrictions?

Again, it depends on the offer.  If the offer is not one of the two common types listed above, we will give the important details along with the offer on the coupon page.

Some offers require you use a specific credit card (Visa, Mastercard, etc.).  Others may require more esoteric restrictions.

Generally, though, coupons are restricted to one coupon use per household.  If there are ten coupons for a particular retailer, you can use each one once.

Buy.com seems to restrict most of its coupons more severely.  They request one coupon use per household, and if you use ANY of their coupons, you cannot use any other.  The automatic checking seems to be more along lines of credit-card number, so using a different card will allow you to use a second coupon.  Some people have said that clearing your browser cookies will do it too, though I've had no success with that method.  If you've discovered anything, please let us know (use the link on the "Contact Us" screen).