Don’t let your list get cold!
This is classic email marketing wisdom. If you’ve got a list of blog subscribers or paying customers, the relationship dies as it gets cold. Once you get subscribers on your email list, stay in contact with them.
This tactic can be especially effective for getting people back to your site/product when they haven’t logged in for a while. There are many services you can use to send these types of transactional emails; customers trigger an automated email message when they don’t login for X days. Remind them about the product and the value it adds to their life.
Whether you’re using fancy automation or not, staying in touch is a simple concept. Give them updates or at least check in just to see how things are going.