Although this may not be of consequence for some of us, parents may spy on us to learn about the other parent. What's even worse? Most of it is legal.
The most common spyware is on our cellphones. It is actually very simple to install and, as long as your parent is paying for the phone, they can read every text, access your call record, view what your screen shows (including facebook and email), and possibly use the microphone on your phone as a listening device.
If you think your parents might be doing this, the easiest thing to do is pop out your phone battery. It will alert them that it is out, but they can't spy unless it is in. I know for a fact that my father has spied and continues to spy on me through my cellphones. I would text my younger brother gibberish like "bologna" or "crumpet with your cup of tea" or "there's bigfoot". Every time a text went through my father's phone would do one of the notification ringtones. He would scowl at my brother and I before turning his phone to silent. This seems like an obvious violation of our privacy, but sadly, until we are 18 it is legal.
Social networking and email is another way that parents may try to spy on you. For example, my parents know my login email for facebook. They could click forgot my password and, because they know me well enough, answer my security questions. There is a trick you can use to tell if one of your parents logged into you facebook. In acount settings, go to security. You will see a list of logins as well as the location. This can be very helpful. Other than that, change your passwords often.
Most parents don't spy on us, but for those of us who are unfortunate should be prepared to take passive resistive action.