You have been using the principles of NLP your entire life, whether you knew it or not. You used them when you were just a baby and unable to talk, yet capable of crying to let your mother know you had made a mess in your diaper, or that you were hungry.

NLP is merely the STUDY of language and the effects it has upon people, whether it be words, tonality, or body language. There is nothing evil about NLP, just as there is nothing evil about a car. It is how it is implimented that causes it to have moral value; just as using a car pick up groceries or visit your girlfriend is a great thing to do, using it to run over school children at a playground is a little unsavory.

NLP was created in the 70's by Richard Bandler and John Grinder in an effort to maximize the effectiveness of communication between people, primarily in a business setting, although it can be used in any setting what so ever. It enables you to more completely understand what others are trying to communicate to you, as well as enhancing your ability to communicate your thoughts to them. This is done by studying the body language that they have and reading the signs that they unconsciously and consciously show in their actions, which often aren't represented in their words, as well a noting the tone changes when they are talking and the words that they use to communicate their thoughts. When you are talking to someone else, you use NLP to choose body language that helps to emphasise what you are trying to communicate (how I sweep my hands in an X as I tell you to forget something, it adds to that and helps you to remove those thoughts), as well as choosing the right tonality (not speaking loud to a person that is upset and instead matching their tone, then slowly raising it up until they feel better, which is a technique known as pacing and leading) and picking the best words to get your concepts across in a way that will connect best to the other person.

There are many many many books and media about NLP, with various schools of thought on how it can be applied, what is morally ok and what isn't. Some say anything is fair game and some say not to manipulate people with it. The trouble comes from the fact that there is no distinct line, because when I use my voice tonality to cheer up a sad person, I have manipulated them in a manner of speaking, so what really makes it so different from planting thoughts of having hot sex with you in her head? That's truly up to you to decide, as no one else can tell you where to draw that line.

There are many many many many many techniques that fall under the umbrella of NLP, just as everyone employs most of them in their day to day lives without being consciously aware of it. As I said, it is merely the study of communication and didn't re-invent the way we communicate, only took note of what techniques are most effective and emphasized the use of them over bad techniques. This is just like how you know many people that have good posture and get more respect than those that have bad posture. Unconscious use of NLP tools is unavoidable and so I personally suggest that everyone familiarize themselves with it, so that they are more capable of choosing how they desire to communicate.