A while back, while visiting my mom, I applied an adhesive webcam cover to her laptop. If you're a frequent webcam user (i.e., you use Skype or similar video-enabled apps), then you'll want to adhere a sliding webcam cover to surface of your laptop, like the one pictured below. Or, if you do not use your webcam, black electrical tape works fine.
A good friend of mine shared a recent New York Times article with me, where the reporter raises the question: Is this is paranoia or just good practice?
Ask yourself this: If you close your window blinds to ward off burglars, is that paranoia or good practice? Any physical security expert will tell you that it's the smart thing to do, as thieves are less likely to hit the house on the street that they cannot see inside.
If you're a high-value target, like Mark Zuckerberg attending a conference, then you definitely want to cover both the mic and the camera. Home users, you should keep your camera covered when not in use. Obscuring the mic certainly cannot hurt.
You be the judge—here is the article: Mark Zuckerberg Covers His Laptop Camera. You Should Consider It, Too.
NOTE: The mic is not the same thing as the microphone input jack port used to plug in an external microphone. If you aren't sure where your microphone input is on your laptop, consult the manufacturer's manual. If you can't find the manual, just Google the make and model number. It's there.