How to check if someone's secretly using your Netflix account

Your Netflix is a personal space. What you watch, when you watch it, and how often you watch it can reveal a lot about you. The last thing you want is someone poking around your account, checking your viewing habits, and drafting off your hard-earned $10.99-a-month for free access. 
And yet people steal Netflix all the time. Whether it's a jilted lover, an old college roommate, or an estranged family member — there are all too many people out there who may be able to use your account