You could email your subscriber and then ask them what they would be needing to learn and know more about.
You could also write to them and tell them that you would be or are working on a product, which would be able to meet their needs.
Create what the client base you have would need.
This would probably be the hardest part - just sitting down and trying to create.
The product would need to be complete, and make sure that you would be doing what you said on your sales letter.
Make sure that you would not be cheating on the creation of your product, as doing so would only be working to your disadvantage in the long run.
Try sending out pre-launch email messages.
You could tell your clients to keep an eye on your company's promotions.
You could also send out some invitations for a joint venture to the other Internet marketers that have subscriber lists, which have similar demographics to the list that you have.
Test your products, merchant services, as well as everything on your business website.
Ask for feedback and suggestions from subscribers to improve or maintain the services that you are offering.
Create a killer sales page, as any good product could flop without a good sales page.
Send an email to everyone who is on your list to let them now that the product is now available.