After understanding the theory of Yoga, you will have to learn the practice from an experienced Yogic Guru. So long as there is the world, there are books on Yoga and teachers also. You will have to search for them with Sraddha, faith, devotion and earnestness. You can get easy lessons from the Guru and practise them at home also in the initial stages of practice. When you advance a bit, for advanced and difficult exercises you will have to stay with the Guru.
The personal contact with the Guru has manifold advantages. You will be highly benefited by the spiritual magnetic aura of your Guru. For the practice of Bhakti Yoga and Vedanta you do not require a Guru by your side. After learning the Srutis for sometime from a Guru, you will have to reflect and meditate alone, in entire seclusion, whereas in Kundalini Yoga you will have to break up the Granthis and take the Kundalini from Chakra to Chakra. These are all difficult processes. The method of uniting the Apana and Prana and sending it along the Sushumna and breaking the Granthis need the help of a Guru. You will have to sit at the Guru’s feet for a pretty long time. You will have to understand thoroughly the location of the Nadis, Chakras and the detailed technique of the several Yogic Kriyas.
Lay bare to your Guru the secrets of your heart and the more you do so, the greater the sympathy and help you get from your Guru. This sympathy means accession of strength to you in the straggle against sin and temptation.
“Learn thou this by discipleship, by investigation and by service. The wise, the seers of the Essence of things will instruct thee in wisdom”. (Gita-IV-34)