It's an annoying thing when anyone of your friends added you to any Facebook Group which you don't want to join, If your friends are doing this a lot you will know through this quick guide how to leave any group and stop receiving notification for it's posts .
The first Step is to go to the Facebook Homepage (NOT your profile), and you will see on the left side of the page the most active groups that you are member of .
To see all the groups please click (MORE) as shown in the image .
Edit Icon which will appear on the left, New menu will appear just Click (Leave Group) .
A confirmation message will appear to say that your friends CANNOT add you to this Group again but if you want you can Rejoin the group again Click (Leave Group) to leave this group permanently .
Another way to leave the group is by visiting the group's page on the Facebook and click the SETTING button on the right of the page then click (Leave Group)
If you want to stay in this group but don't want to receive any notifications from this group, Click (Notifications) on the right of the page and then Click (Off) .
Now you will not receive any notifications from this group but you can visit it and see the new posts there .