How do I track re-visitors on my website to push promos?

I am a newbie and my requirement is to push promos to re-visitors (who didn't order anything on their first visit).

I couldn't find much help online(other than articles on google analytics).

Any help or direction towards right sources is appreciated.

Solution

Depends on how you plan to store data. But as a cheap and simple way, you can accomplish this with javascript and setting localStorage.