Lots of people will already be in the know about this "secret", but it may come as a curveball to some…

If you are into creating products to sell (eg eBooks, templates, software, scripts) then you need to realise that existing customers are the easiest people to sell to.

1. They have already bought from you
2. They most likely trust you
3. They know that they will receive good Customer Service
4. etc etc

The Secret
So, when making a product for sale, make sure that it ties into at least one of your previous products! That's the secret. Or rather the "not so secret".

In reality, it's not and never has been a secret at all but many won't have thought to create and market products specifically for prevous customers.

Example
A good example of this is my new "Site Builder" product. One of the main features of this ties directly into my previous PLR Manna "Headers/Middles/Footers" tool. I have made 3 sales in the last few days, which are all from purchasers of the Site Builder. OK, so 3 sales at $97 each is no great shakes, but it's still an extra $291 which is rather nice.

In conclusion
Create your new product to tie in with a previous product. Show how easy it is to use both together, then send an email to previous buyers to let them know of your latest product.