deshah bandhah chittasya dharana - Patanjali
(Concentration (dharana) is the process of holding or fixing the attention of mind onto one object)
Attention leads to concentration (dharana)
Concentration leads to meditation (dhyana)
Meditation leads to absorption (samadhi)

This chapter deals with practices that hone such attention and hence the ability to concentrate. This leads to stability and clarity of mind, which is necessary for much subtler experiences of meditation and absorption.

Before we dwell into the practices, Lets dissect the need for it. During all these yogic practice seeking higher levels of experiencing the life and its manifestations, from time to time, there arise obstacles. Patanjali enlists 9 such obstacles that are to expected.

vyadhi styana samshaya pramada alasya avirati bhranti-darshana alabdha-bhumikatva anavasthitatva chitta vikshepa te antarayah - Patanjali
Nine kinds of distractions/obstacles are naturally encountered on the path. They are;
1.) Physical illness, 
2.) Mental Dullness
3.) Doubt - Like doubting if this all a scam to propagate something like a religion, etc. 
4.) Negligence - Lack of attention to pursue it to the fullest (to samadhi)
5.) Laziness - Both physical and mental. Watching TV is more pleasing to the mind than contemplation.
6.) Cravings - Desire for the worldly things overtaking the determination on the path
7.) Misperceptions - deriving incorrect assumptions
8.) Failure - in attaining the defined next stages in practice, like satori (glimpses of absorption)
9.) Instability - failure to maintain the levels attained. Falling back from ability of perform an asana pose.

Once we know these 9 obstacles are to occur, it provides a comfort and ability to see through it. When one succumb to these obstacles, these four consequences occur.

duhkha daurmanasya angam-ejayatva shvasa prashvasah vikshepa sahabhuva - Patanjali
From these obstacles, there arise four consequences:
1.) Pain - Physical and psychological
2.) Sorrow - Frustration, sadness, dejection, 
3.) Unsteadiness - restlessness, shakiness, or anxiety.
4.) Breath Irregularity - irregularities in the exhalation and inhalation of breath.

To tackle all these 9 obstacles and their 4 consequences, there is a single anecdote, i.e., ekagrata meaning one-pointedness of the mind.

tat pratisedha artham eka tattva abhyasah - Patanjali
(Practicing one-pointedness prevents/shatters the distractions and its companions)

Lets discuss the actual tools (practices) to sharpen the concentration.

Trataka, one of the shat-karmas (the six kriyas of purification / detoxifying) is a best tool to start with.
1.) Dark place is needed and hence it is recommended to preform before sunrise or after a couple of hours after sunset in a room with the air-flow is normal so that the flame is mostly steady.
2.) Arrange a candle or a lamp so that the flame is at eye level in height and arm-length away from the eyes.
3.) Get seated in a comfortable position, Padmasana, Vajrasana, siddhasana or sukasana; But the spine and neck needs to be erect and you should be able to hold the posture without any movements for at least 24 minutes.
4.) Steady the breath by focusing on the exhalation and the natural retention for 5-10 breaths.
5.) Start Gazing at the flame without blinking until tears are flowing over the cheeks. Start doing it for 6 minutes and increase it to 24 minutes at your comfort level.

Trataka can also be performed on contrasting dot in a wall, moon, star and with a little practice one can bring the object to focus with closed eyes.

In the beginning, it'll feel impossible, but with very little effort, in a couple of days you'll be able to do it effortlessly. First 2 minutes needs quite an effort, once tears starts flowing, it automatically lubricates the eyes and its easy to hold the gaze without blinking. Breathing and blinking are the only two external activities we humans do both intentionally and unintentionally.

The actual practice of dharana (concentration) involves contemplation on a single object. For an outsider, it might look like dhyana (meditation), but they are quite different. Dharana involves explicit contemplation on a single object, while dhyana transcends upon the person and he/she is devoid of any thought.

Such Contemplation can be practiced on 9 different things.
1.) Four attitudes in dealing with people (Friendliness, Compassion, Admiration, Neutrality). These are extroverted by nature.
2.) Five aspects to focus on (breath awareness, sensation, inner luminosity, stability of mind, stream of thoughts). These are introverted.

Many schools of meditation emphasize only one method such as meditation on kindness, breath, or an external object and some combines two like vippasana (breath awareness and sensation). It is recommended to practice all 9 for several days before finding the few that resonate with your being.

Attitudes in dealing with people, is more of a course correction in daily livelihood. Most of our response to such situation are involuntary and automatic. There is quite a bit of unawareness and the response is not mindful. In yoga, acceptable attitudes are encapsulated into these four, which helps us evolve harmoniously.

maitri karuna mudita upekshanam sukha duhka punya apunya vishayanam bhavanatah chitta prasadanam - Patanjali
(The mind becomes purified by cultivating feelings of friendliness towards those who are happy, compassion for those who are suffering, goodwill towards those who are virtuous, and equanimity towards those we perceive as wicked or evil)

1.) Maitri (Friendliness): When we come across joyous people, often we unintentionally have a negative attitude towards them. This may not be a full repulsion, but realizing there is a trace of negativity and consciously encountering it and cultivating the positiveness will generate a great sense of inner calmness. Once experienced it is delightfully contagious and has the ability to wipe away all the negative traces in a short time.

2.) Karuna (Compassion): Most believe they are compassionate until they find themselves struck in a traffic because a fellow human met with an accident. Even simple things like, when an elderly person asks you for a glass of water when you are watching your favorite sitcom, all the compassion is out the window. Just taking note of such moments even after they happened is a good start. Slowly, the moment of realization will occur early and soon you become aware of the lack of compassion during the act and once the awareness occurs before your response, you are fully compassionate.

3.) Mudita (Admiration): When we encounter a person who is virtuous or benevolent, most feel jealous or inadequate and get into a self-loathing mode. Redirecting all these negative energy into pure admiration for that person is not an easy task. A good start would be to watch the inner turmoil that happens without identifying ourselves with it. This will lead to neutrality and slowly evolve into an honest admiration and goodwill for that person.

4.) Upekshanam (Neutrality): While dealing with someone dishonest, cruel or a very evil-intent person, a strong sense of anger and aversion arise. Such response hurt oneself the most. To counteract such negative emotion, cultivation of feeling of neutrality or equanimity is suggested. This might make one feel approving the actions of the person involved. But cultivating such neutrality will open the ways to cause the necessary change.

These four attitudes are practiced in day-to-day activities involving social relationship. Constantly observing oneself and consciously being away of the attitude towards others for months and years will ensure we are devoid of all the negative traces and successfully transformed all the attitudes into one of these four prescribed attitudes.

Five aspects to focus on is a very practical tool and can be practiced in cycle when you sit down for your hourly mediation every day. As obvious it is, it is introverted and practiced in solitude.

prachchhardana vidharanabhyam va pranayama - Patanjali
(The mind is also calmed by regulating the breath, particularly attending to exhalation and the natural stilling of breath that comes from such practice)

1.) Breath awareness is one of the finest methods prescribed for mind stability. Observe the natural flow of breath. ensure the transition between inhale and exhale is smooth and not abrupt. Consciously fine tune the transition. Once this is mastered, work on elongating the exhalation. Exhale slowly for twice the time it takes to inhale the same amount of breath. Watching this exhalation and observing the natural pause that occurs before next inhalation is extremely pacifying.

vishayavati va pravritti utpanna manasah sthiti nibandhani - Patanjali

(The inner concentration on the process of sensory experiencing, done in a way that leads towards higher, subtle sense perception; this also leads to stability and tranquility of the mind)

2.) Sensation - the process of keenly observing the sensory perceptions is the core principle of a key technique devised by Gauthama Buddha, known as vippasana. At first the practitioner might be more inclined to pursue the object of sensation. This should be consciously diverted to the process of sensation itself. Like when you feel a touch, pain, heat, cold or sweat, observe how the sensation feels like and how it arises and be gone. Quickly, move on to the next without any attachment (like/dislike) towards the sensation itself. This is one of the common practice amongst sages of the east.

vishoka va jyotishmati - Patanjali
(Or concentration on a painless inner state of lucidness and luminosity also brings stability and tranquility)

3.) Concentration on inner state - Focus on the heart charka (thymus gland) located exactly in the center between chests. Imagine a palm size luminous glow in this spot and stay focussed with every breath irrespective of thoughts and impressions arising in the mind.

yatha abhimata dhyanat va - Patanjali
(Or by contemplating or concentrating on whatever object or principle one may like, or towards which one has a predisposition, the mind becomes stable and tranquil)

4.) Stability of Mind - This is a little advanced as you are consciously tricking your mind temporarily. This is where idol worship comes into picture. Pick any objective reference of devotion and convince you mind that it is as calm and stable as that object's. With little practice you transcend into this state of tranquility with ease.

svapna nidra jnana alambanam va - Patanjali
(Or by focusing on the nature of the stream in the dream state or the nature of the state of dreamless sleep, the mind becomes stabilized and tranquil)

5.) Consciously focussing on stream of thoughts/dreams will stabilize the mind. This method is commonly prescribed by wise, but not easily understood by a common man. Generally, one tends to start responding to a thought with judgement and influence the successive thoughts. With a little practice, this involvement can be withdrawn and one can witness the stream of thoughts as just an observer. This process has a great calming effect and helps a person to realize the pattern of mind and take control of it with ease.

These methods are very critical tools in tuning the concentration which exemplifies the sensitivity of a practitioner to develop extra-sensory perceptions to experience the intensities of dhyana and samadhi.

Next: Yoga: 7. Dhyana (Meditation)