Right, having a list is naturally going to help you...

Create something, related to the product, to give away before the launch. That way you'll have a very targeted list, and if your freebie was good, people should be more likely to buy from you.

Personally, I would do an interview with the product creator and talk about the product. Get him to give away a couple of the techniques he uses in the course... Better yet, if the product has software involved that makes things faster and easier, get the product creator to explain how to do the process manually.

That way it's good content for the list, it's useful info that's more than likely free to implement, but when they realize how time consuming it is , they'll be biting at the bit to buy the software on launch day.