Many people use the term "Mind Control" for different things. Actually it is a broad meaning having different types. Mind control means to take control of the mind. The question is whose mind is being controlled?
There are many mind control techniques. These draw upon different sciences and methods. So we have to clarify whether we speak for controlling our own mind or the mind of other people.
So if someone wants to affect and control the thoughts of others, then he must learn hypnosis techniques and NLP (Neurolinguistic programming). Although NLP is a toolbox focused on self development it can help with understanding what type of personality the person you want to affect is.
For example conversational hypnosis is a very powerful hypnosis technique for ideas and emotions manipulation. While you seem to talk naturally to the other person you carefully "seed" a specific thought into their mind. This is undetectable to the other person (this method is also called covert hypnosis) as you actually contact with their subconscious mind.
After a while the thought you planted comes up as a new idea to the other person. While they believe that they thought this by themselves, in reality you told them what to think. So in this way you can manipulate and control their mind.
Traditional hypnosis from the other side requires the consent of the other person so to allow you to hypnotize them and plant thoughts in their subconscious.
Another hypnosis technique which seems as mind control is the Stage Hypnosis. This is a technique used by showmen hypnotists in order to control a "volunteer" participant. There is a debate if this is truly a mind control technique or a fake technique.
Now for those who refer to mind control as a way to control their own mind, there are plenty techniques available. Some popular ones are self hypnosis, the Silva method, Meditation and brainwave entrainment. In the latter, control has different meaning than the first two.
In self hypnosis a person tries to induce their mind into hypnosis. This usually happens with detailed visualizations activating the right hemisphere and lowering the brainwaves frequency. These visualizations can show an easy metaphorical way of achieving their goals, quitting bad habits, losing weight and more.
Self hypnosis may be guided or unguided. Guided means that a person listens to a prerecorded instruction from a hypnotherapist in order to get into trance and be hypnotized. Internet is full of such products which are aimed to specific purposes. Some very popular include quitting smoking, losing weight, relaxing, helping with sexual problems and more.
The unguided type is more difficult and involves only the person's thoughts for inducing them into trance and hypnosis. Visualizations are mainly used for this reason and it is required that the person will be stay focused on the technique.
A similar technique is the Silva mind control method. Actually Silva method is being taught on seminars and involves easy and specific exercises to achieve mind control. One of them is the three fingers technique which boosts memory on demand.
Meditation approaches mind control differently. While the previous mind control techniques activate the right hemisphere and the imagination of the individual, the goal of meditation is exactly the opposite; to shut the thought production. There are hundreds meditation techniques. One easy one is concentration meditation where a person tries to focus his attention to an internal (e.g. breathing) or external (candle flame) fixed point.
Brainwave entrainment is also a mind control method with different meaning. Here the concept is to control the frequency of the brainwaves in order to produce specific brain states. There are many types of brainwave entrainment. The most popular one is using binaural beats. A binaural beat is a sound which is formed in the brain when two slightly different tones are presented to each ear through headphones. With brainwave entrainment methods the brain follows the frequency of the external stimulus. In other words the frequency of the brain alters to the frequency of the beat, resulting to altered states of consciousness.