Do you have a need to discount a particular product variant in your store?
First, go to Promotions | Discounts and click Add New
Give your Discount a descriptive name
Choose Discount Type: Assigned to product variants (SKUs)
Either give a discount percentage or dollar amount.
Choose Start and Stop dates for the discount code.
Check Requires coupon code.
Enter your coupon code unique id
Enter your limitations for your discount/coupon.
Click Save
Go to Catalog | Products | Manage Products and Edit your product to be discounted.
Click Product Variants and Edit the variant to be discounted.
Click the Discounts tab and select the previously created Discount.
Article ID: 2, Created On: 12/6/2011, Modified: 12/6/2011