Check your Settings > Security and Login > Where You're Logged In . If you see a device or location you don't recognize, that is the most definitive "telltale" sign.
Here is an analysis of what these "telltale" signs actually are, how scammers use search operators to find targets, and how you can solidify your account security. 1. Understanding the Search Operator site%3afacebook.com+telltale++hack
Go to Settings > Apps and Websites . Remove any old games or "Which Disney Character Are You?" quizzes, as these often have permissions to post on your behalf. Check your Settings > Security and Login >