How can one achieve "siddhi" in Hinduism?

Question

I have heard recently about Guru Siyag who chanted 3 lac Gayatri Mantra(I don't know exact number) and attained "siddhi" according to him and his followers. Check out any youtube video of Guru siyag. He says he removes cancer from people who follows his "sidhdha" meditation!!

My question is how can one achieve "siddhi"? How many types of "siddhi" are? Is it true by chanting mantras "siddhi" come?

Does God gives supreme powers? is this "siddhi"? How and When? If I chant some x mantras will I be able to hold powers from GOD? How many mantras in day?

Answer 1

Yoga Sutra of Patanjali gives methods of achieving Siddhi (4.1):

जन्मौषधिमन्त्रतप: समाधिजा: सिद्धय:॥ १॥
janmaushadhimantratapahsamadhijah siddhayah
"The Siddhis (powers) are attained by birth, chemical
means, power of words, mortification or
concentration."

Here is Swami Vivekanandas commentary on this verse.

Sometimes a man is born with the Siddhis, powers, of course from the exercise of powers he had in his previous birth. In this birth he is born, as it were, to enjoy the fruits of them. It is said of Kapila, the great father of the Sankhya Philosophy, that he was a born Siddha, which means, literally, a man who has attained to success.

The Yogis claim that these powers can be gained by chemical means. All of you know that chemistry originally began as alchemy; men went in search of the philsopher’s stone, and elixirs of life, and so forth. In India there was a sect called the Rasayanas. Their idea was that ideality, knowledge, spirituality and religion, were all very right, but that the body was the only instrument by which to attain to all these. If the body broke now and then it would take so much more time to attain to the goal.
For instance, a man wants to practice Yoga, or wants to become spiritual. Before he has advanced very far he dies. Then he takes another body and begins again, then dies, and so on, and in this way much time will be lost in dying and in being born again. If the body could be made strong and perfect, so that it would get rid of birth and death, we should have so much more time to become spiritual.
So these Rasayanas say, first make the body very strong, and they claim that this body can be made immortal. The idea is that if the mind is manufacturing the body, and if it be true that each mind is only one particular outlet to that infinite energy, and that there is no limit to each particular outlet getting any amount of power from outside, why is it impossible that we should keep our bodies all the time? We shall have to manufacture all the bodies that we shall ever have.
As soon as this body dies we shall have to manufacture another. If we can do that why cannot we do it just here and no, without getting out? The theory is perfectly correct. If it is possible that we live after death, and make other bodies, why is it impossible that we should have the power of making bodies here, without entirely dissolving this body, simply changing it continually? They also thought that in mercury and in sulphur was hidden the most wonderful power, and that by certain preparations of these a man could keep the body as long as he liked.
Others believed that certain drugs could bring powers, such as flying through the air, etc. Many of the most wonderful medicines of the present day we owe to the Rasayamas, notably the use of metals in medicine. Certain sects of Yogis claim that many of their principal teachers are still living in their old bodies. Patanjali, the great authority on Yoga, does not deny this.

The power of words. There are certain sacred words called Mantrams, which have power, when repeated under proper conditions, to produce these extraordinary powers. We are living in the midst of such a mass of miracles, day and night, that we do not think anything of them. There is no limit to man’s power, the power of words and the power of mind.

Mortification. You will find that in every religion mortifications and asceticisms have been practiced. In these religious conceptions the Hindus always go to the extremes. You will find men standing with their hands up all their lives, until their hands wither and die. Men sleep standing, day and night, until their feet swell, and, if they live, the legs become so stiff in this position that they can no more bend them, but have to stand all their lives.
I once saw a man who had raised his hands in this way, and I asked him how it felt when he did it first. He said it was awful torture. It was such torture that he had to go to a river and put himself in water, and that allayed the pain for a little. After a month he did not suffer much. Through such practices powers (Siddhis) can be attained. Concentration.
The concentration is Samadhi, and that is Yoga proper; that is the principle theme of this science, and it is the highest means. The preceding ones are only secondary, and we cannot attain to the highest through them. Samadhi is the means through which we can gain anything and everything, mental, moral or spiritual.

योगश्चित्तवृत्तिनिरोध: ॥ २॥ (Patanjali sutra 1.2)
yogashchittavrittinirodhah
"Yoga is restraining the mind-stuff (Chitta) from
taking various forms (Vrttis)"

Hence the key to achieve siddhi through Yoga lies in mind control (all other methods described are forms of mind control).

Answer 2

There are in fact more than one question in your question viz:

1.How many types of Siddhis are there?

2)How to achieve them?

3)What is Mantra Siddhi & how to achieve it?

How many types of Siddhis are there?

The Linga Purana describes the primary Siddhis as follows

A successful Yoga Practitioner is endowed with ‘Dasha Siddhis’viz. Pratibha, Shravana, Vaarta, Darshana, Aaswaada and Vedana. Jnaana Pratibha is the Siddhi of knowing about a Vastu or Vyavahar or of a thing of past, present or of future; this Siddhi would infuence or impress others. Shravana Siddhi enables a Yogi to hear or understand any kind of sound or conversation or a happening irrespective of distance or time. Vaartaa Siddhi facilitates the experience of Pancha Tanmatraas of sabda-sparsha-rupa-rasa and gandhas. Darshana Siddhi is the ability to perceive or vision of any thing irrespective of time and distance limitations. Aaswaada Siddhi enables tasting any substance and Vedana Siddhi is the power of sparsha to experience the shape, form or a feature of a person or thing.

More kinds of Siddhis are also described on the same page as follows:

In fact a Maha Yogi is stated to possess sixty four kinds of Paisachika, Parthiva, Raakshasa, Yaaksha, Gaandharva, Aindra, Vyomatmika, Praajaapatya, Brahmaadi Siddhis but he should discard all such powers in the quest of Shivatwa. Such Siddhis range from assuming any type of Swarupa of fatness, slimnes, childhood, youth, old age, man, woman, any specie of a bird-animal-reptile, mountain, water body and so on; ability to lift mountains, drink up an ocean, flying on sky, passing through a needle’s eye and endless such miracles. [The normal Siddhis are Anima (miniaturising), Mahima ( Maximising), Prakamya (Visioning and Hearing), Isatwa (Rulership), Vasitwa (Self Control), Kama Vasitwa (ability to fulfill desires), Doora Shravana and Doora Darshana or distant vision and hearing, Parakaya Pravesha or ability to enter other’s bodies; ‘Devaanaam Saha kreedanam’ or playing with Devas, Yatha Sankalpa Samsiddhi or instant fulfillment of desires,Triloka Jnaana or knowledge of the happenings of Three Lokas; Control of heat and cold, Paraajaya or invincibility and so on.]

How to achieve Siddhis?

The method of obtaining Siddhis is by practising "Ashtanga Yoga".The description of Ashtanga Yoga is found on the same page from where i quote:

To control the activities or goings on in the mind is Yoga. The Ashtanga or Eight-Limbed Yoga comprises of Yama- Niyama- Aasana- Pranaayama- Pratyahara-Dharana-Dhyana-Samadhi. Yama is denoted by good behaviour comprising Ahimsa (Non-Violence), Satya (Truth), Asteya (stealing), Brahmacharya (avoidance of sex) and Aparigraha or Excessive acquisition. Basic Niyamas is in fact an extension of Yama: To refrain from hurting or torturing co-Beings physically or mentally is Ahimsa; to convey whatever is seen, heard, and believed is Satya unless it does not hurt any body is known as Satya; to desist stealing of other’s property by deed, thought or otherwise is called Asteya; to negate from relationship with another female or in respect of a female wih another male, excepting the wedded woman or man as the case may be and this should be observed by vision, thought or deed is called Brahmacharya or celibacy; and to abstain from excessive acquisition of materials far and above one’s needs in the short run of time is stated to be Aparigraha. Besides the above General Principles, Niyamas also involve the specific deeds viz. Shoucha or Physical Cleanliness,Yagna-Tapa or meditation, Daana or charity, Swadhyaya or Memorising or Reciting the Scriptures, Indriya Nigraha or Control of Physical Limbs, Vratas like Chandrayana as also or to perform formal worship directed to specific Devatas and purposes,,

What is Mantra Siddhi & how to achieve it?

Mantra Siddhi is a devotee's full control over the wholesome power of a Mantra & is obtained upon reciting a particular Mantra for a fixed number of times with certain other constraints being imposed .First and foremost you should get your Guru to obtain a Mantra.Or else you can pray to your Ista Devta and start.Rest is quoted from this page. Mantra Siddhi is also called Mantra Purasarchana.

METHOD OF MANTRA PURASCHARANA

The repetition of a Mantra with rigid spiritual observances a fixed number of times to obtain quick spiritual progress is known as Mantra Purascharana. It can be performed for material progress too. The practitioner should observe certain rules and undergo strict dietetic discipline to ensure quick Mantra Siddhi.

During the Purascharana take only fresh vegetables, fruits, milk, roots, barley and Havis-Anna (rice cooked with ghee, sugar, milk). A Sadhaka can live on pure Bhiksha (alms) also. If you can live on milk alone during the period of Purascharana it is highly laudable. You can have Mantra Siddhi even by repeating the Mantra a lakh of times.

Select any holy place of pilgrimage on the banks of sacred Ganga, confluence of rivers, mountain valleys of charming scenery, temples, Tulasi gardens, below Asvattha trees or convert a portion of your house into a temple by keeping the picture of the Lord, burning incense etc., and by suitable decorations. Purascharana done in holy places has a benefit hundred times superior to that done in one's own house.

You can select any Mantra for Purascharana. Your Guru Mantra or Ishta Mantra is the best. Sandhya time, sunrise, sunset, midday are all recommended for Japa. Repeat the Mantra as many lakhs of times as there are letters in the Mantra. You can do half of that number. In no case the number should be less than a lakh........

After completing the Purascharana perform Homa th the number of Japa, Tarpana (water libations) th the number of Homa, Marjana (sprinkling) th the number of Tarpana and feeding of Brahmins th the number of Tarpana. You can do feeding and charity according to your capacity if you cannot adhere to the above strictly.

It is recommended that you read the whole article and not just the portions i have quoted from it.