It is very simple, you follow all the blog sites and announcement channels for most of the exchanges.
And in that manner, you will get to see those coins that are going to be supported and listed on those exchanges.
Yes this is one way to know such. Constant visit to the exchanges, you can have an idea. So you can save your choice exchanges on your home screen for easy view and access.
All the social media accounts too. Most of the announcements are also there as they also create a blog about their new listings. It won't take you a lot of time just to follow and check them from time to time. If you have spare time, visit them all at once or those exchanges that you're mostly using. And also to the project that you're following, you will get hints from what's happening to the development and where they're about to be listed.