Following someone is generally a bad idea, but it doesn't hurt to be aware of how it's done so you can protect yourself where possible.
It's worth pointing out that following someone is not only a gross invasion of privacy, it's also potentially illegal if it's interpreted either as stalking or harassment. Many of the techniques in this article are used by private investigators, but even so it's a grey area at best. This information is primarily to help get you in the mind of someone who might be following you so you can learn to notice the signs. We don't recommend trying this yourself.
Learn Their Patterns Ahead Of Time
Depending on how closely you know the person you want to follow, this may be easier said than done. However, the more information you have about your target's habits, the better able you'll be to know where they're going. We've already covered how you can research someone online without too much trouble. People may not always put their most incriminating secrets on Twitter, but a home address, a work address and knowledge of nearby supermarkets and schools can help you figure out what paths a person might take during a normal day, as well as what would be out of the ordinary.
Get Gear To See (Or Record) From Afar
The general rule when following someone is that if you can see them they can see you. However, if you're using a video camera with a zoom lens, or a pair of binoculars, your chances of seeing without being seen increase dramatically. This is particularly essential if you want to observe someone for longer than a couple of hours. Most times, while conducting surveillance, you may be sitting for hours or even days waiting for your target to do something. This is part of why it's handy to know your target before you get out in the field.
Keep Your Distance, Particularly While Driving
In the movies, you might see the hero of the story discover that he's being followed by glancing in his rear-view mirror and seeing a black cadillac being driven by a guy in dark sunglasses. This is rarely the case. Unless the person you're following is committing some crime while behind the wheel, you probably don't have to be directly behind them. Just following closely enough to know where they're headed is sufficient. Of course, if your target makes four left or right turns in a row, the jig is probably up.
This strategy extends to any location. If your target pulls into a car park, don't follow them through every aisle. Park in a place where you have a good view of the entry to the store, without being obviously noticeable from a distance. If you need to watch someone's home, don't park across the street. Make copious use of that zoom lens and park far away. Most people don't have the instinct (or the eyesight) to keep a close eye on anything very far away from them.
Use Mirrors, Car Parks and Public Places To Your Advantage
Your car has plenty of mirrors plastered all over it, which makes it possible for you to see (and record) in a variety of directions. Most people, however, will only expect that anyone watching them in a car will be doing so from the front seat, staring directly ahead. If you plan to watch someone from a distance, point your vehicle away from where you expect them to be and watch them through a mirror. Obviously, you could still raise eyebrows if you're pointing a camera at your rear-view mirror, but you're less likely to get the attention of your target if they only see the back of a head rest.
Depending on what type of act you expect to catch your target in, your best bet for seeing them is either at or from public locations. While the law is more nuanced when you're dealing with following someone, the same general rules apply as regular photography: if you can see it, you can shoot it. This means that if someone is hanging out on their front lawn and you happen to record it, it's probably fair game (disregarding any controversy over stalking or harassment, but we'll talk even more about that below).
Get Up Close and Personal With Disguised Cameras
I have some bad news for people who are worried about Google Glass making it easier to spy on people without them noticing: it's already easy, and you haven't really noticed. If you have a need to get inside a building and find out what a person's up to, your best bet is to make use of a hidden camera.
ThinkGeek sells a model of the quintessential pen camera that shoots 720p video for a mere $US50, and you can get even cheaper models. However, the hidden cameras don't stop there. Here are just a few everyday products that you can buy with hidden cameras built in:
In short, whether it's something you need to carry around on your person, or if you want to place something in your own home or office to keep track of what goes on, there is no shortage of options for cameras that no one could spot. Of course, that's just things you can buy from a store. You can also make your own tiny Wi-Fi cameras for comparatively cheap and place them in whatever object you'd like.
Recording someone inside a private establishment, however, becomes much more of a legal grey area. If you want to avoid getting in trouble, you should probably avoid doing much (or any) recording inside a building you don't own or have permission to record in
Avoid Legal Issues (Mainly by Not Doing Any of This)
Keep in mind that many of the techniques described here are questionably legal at best, particularly when it comes to recording. It's impossible to say for sure that you won't end up breaking some law by following someone with these techniques, and you'll almost certainly do so if you record it. However, that doesn't mean you can't be aware of how things are done. The important thing to keep in mind is that if you're outside, near public areas, or even visible from a public space, you can probably be seen and recorded.
This post is part of our Evil Week series at Lifehacker, where we look at the dark side of getting things done. Knowing evil means knowing how to beat it, so you can use your sinister powers for good. Want more? Check out our evil week tag page.