So far, the first sutra in chapter 2 has told us that all we need to do to transform ourselves and find enlightenment (Samadhi) is to practice with a burning intensity (tapas), to study the texts that have described this path in detail and to look inward to see how we are progressing on the path (svadhyaya) and to surrender to a higher power (ishvara pranidhana).

In the second sutra it tells us that why we should do these things and that is because these practices remove obstacles and lead to Samadhi.

The third sutra enumerates what these obstacles are: avidya or seeing things incorrectly, asmita or the ego, raga which is attachment to pleasure, dvesha which is avoidance of painful experiences and abhinivesha which is fear of death or clinging to life.

Sutras 4 - 9 define each of these obstacles in more detail.

Yoga Sutra 2.10 – Te pratiprasavaheyah suksmah
te – these
prati – in opposition, against
prasava – procreation, generation (prati prasava = involution)
heyah – to abandon, desert, relinquish, emit, renounce, abstain
suksmah – subtle minute, delicate
These subtle afflictions (ego, attachment, fear) are to be minimized and eradicated by a process of involution.

Yoga Sutra 2.11 – Dhyannaheya tadvrttayah
dhyana – meditation, reflection, attention, observation
heyah – to abandon, desert, relinquish, emit, renounce, abstain
tad – their
vrttayah – fluctuations, movements, operations
The fluctuations of consciousness created by gross and subtle afflictions are to be silenced through meditation.
Tapas removes the gross afflictions, svadhyaya removes the subtle afflictions and ishvara pranidhana removes the most subtle obstacles.

How to Meditate.
The first chapter of the Yoga Sutras gives seven suggestions on how to meditate:
Y.S.1.33 -  Be happy for the happiness of others, be compassionate when they are not happy, When they are vitruous, be encouraging and be indifferent when they are not.
Y.S.1.34 - Use an object of meditation such as a candle flame, a flower, a deity or a crystal to focus the mind.
Y.S.1.35 -  Practice Ujjayi breathing techniques.
Y.S.1.36 -  Focus on the light within your own heart, the seat of the soul.
Y.S.1.37 - Contemplate sages whom you admire, who were calm and tranquil and free from desires and attachments.
Y.S.1.38 - Learn the technique of lucid dreaming
Y.S.1.39 - Or, if any of these techniques don’t work, meditate on anything you choose.

I once had a yoga student who told me that a teacher told him that he was meditating wrong. This was several years before I had read these Yoga Sutras, but I strongly believed that what he was told couldn’t possibly be true. There are lineages that have developed particular techniques that have proven track records, but there is a great variety from one lineage to another. I believe, and these sutras seem to corroborate that, if one system of meditation does not work for you, try another until you find a practice that you can maintain.