We've got a regular shipping method, and a fast, premium shipping method.
The customer can choose, and pays extra for the premium..
I want to offer free shipping via coupon for the regular shipping method only. The problem is that both shipping methods are free when I set free shipping on a coupon.
I would prefer writing some code rather than finding, and purchasing and extension. Can anyone help me locate the file in which to put the code, and what the code should be??