It really bothered me to sometimes not see a new thread in one of my social groups in a timely manner, just because I'd so often forget to navigate to it(!) Lol. Turns out there's a quick and easier-to-remember way! You can have a notice come up right on your profile page to alert you! (Shows up just under "Subscribed Threads" there.) Because (hopefully! ) I'm not the only person who didn't realize this, here's how to:

Go to the social forum posts page.
Pull down the menu for "Forum Tools" (upper right) and click on "Subscribe to this forum". Et voila!

Leo... I think you can have your notifications set to email as a further step...(in fact, I believe the option comes up after you hit "subscribe to this thread" on the pulldown menu. If that doesn't work, let me know (I don't do the email notifications, so I'm just going from memory on that part. )