It's all so simple to sell tons and tons of products when you have a list, but how do you get started on building a responsive and targeted list?
In my experience it's not quite as simple as your statement suggests <grin>, there's still a lot to learn to do it well.
But you're on the right track, in my case and many others I know of, building a list then selling to it has shown itself to much more productive then just advertising and going for a sale directly.
How to do it?
1) Search Google for one of the many courses on Listbuilding. Just make sure the author is recognised as an expert in the field. Paul Myers comes to mind as one.
2) My own newsletter has a very extensive video tutorial section on Listbuilding, but a word of warning, it's not a lightweight treatment of the subject, you will need to take some time to *study* it, start putting it into practice, then review it again, perhaps many times. Worth the effort though.