View of Ayatullah Khomeini
"There are two meanings of the word Istikhara ‑ one of them is the actual meaning and more than all the other types has been mentioned in our narrations (ahadith) and is the most common, and this is simply supplicating and asking Allah for the best.
This type of Istikhara has its roots in supplicating (to Allah ) in all actions that a person performs, and is not only admirable, but is recommended (Mustahab) in Islam.
The other meaning of Istikhara is when a person is confused and perplexed about whether to perform an act or not, such that it (that act) is not something that Allah ?t has ordered us to perform such that His guidance would be there nor that our intelligence could help us to decide if it is good or bad. If there is no way for a person to decide whether to perform a task or not, and in the state of confusion and uncertainty, instead of simply guessing and performing the act, the person seeks refuge with the AllKnowing Allah , who all in distress turn towards and seek council from.
Allah will either guide him through his heart and thus reveal to him which path to choose, since in reality, He is the Changer of hearts (in relation to the `spiritual Istikhara').
Otherwise, He will place the person's hand on a certain part of the Tasbih. (if he is performing the Istikhara by way of the Tasbih beads), or he will guide His servant's heart by the Qur'an (if he is using the Qur'an for his Istikhara).
Is it not that a person who is confused, after using his own common‑sense and asking advice and help from others in need of guidance so as to open his path? Can it be that a person, whose `lamp of thinking' has gone dim and has sought help from others around him not in need of advice and guidance?
In one of the verses of the Qur'an, Allah after mentioning and counting all of His powers and the blessings which He has showered says: "Or; Who answers the distressed one when he calls upon Him and removes the evil? 
However, there are examples that people who are against Istikhara mention, such as the incident in which there was a girl who liked a young boy and in all ways, were compatible with each other, but after talking with one another, the Istikhara was performed and it came out 'bad' and the discussion ended there. Another example is about a person who wanted to purchase a house. Everything was fine and in all ways, the house was ideal ‑ he performed an Istikhara and it came out bad, so he decided not to purchase the house.
It is clear that the reply to them and thousands of people like these regarding the Istikhara (and the proper use of it), is that in instances such as these, only one who has no intelligence, who is defiant, and who does not have a correct understanding of the Istikhara would perform it in these instances.
It also goes without saying that the ahadith that have come to us with regards to the Istikhara have not promised us that we will reach our goal without any troubles or difficulties. Rather, that which has been promised is that whosoever asks Allah for good, will be granted good. If it is good for the person in his worldly life, then he will be granted his wish; and if it not, then it will be stored for him and bestowed upon him in the next world."
`Allamah Sayyid Muhammad Husayn Taba'taba'i
"When a person makes the intention to perform a certain act, then he has no choice but to investigate concerning it, and as much as he is able to, he must ponder and think ‑ using the power that Allah has given him ‑whether or not to do that particular thing.
In the event that he is not able to come to a conclusion (if what is good for him is in that act), then he must ask others for advice and let his decision lie on the advice of others ‑ those who are able to offer advice and have the ability to distinguish between good and bad.
He should rely on their rationale to come to a conclusion whether to proceed with an action or to leave it. If this route too does not produce results, then he is left with no other alternative except that he pleads to His Lord and asks Him for guidance to what is truly best for him.
In reality, this is the Istikhara. This must not be referred to as `gaining knowledge of the unseen' or an incursion on Allah's guardianship and mastership upon us.
In summary, there is no responsibility on the religion when one performs an Istikhara, since the Istikhara does nothing except determine which way a person should act. The Istikhara does not change the rules of Allah nor does it inform the servant of Allah that what is hidden behind the curtains of Allah's knowledge. The only thing that an Istikhara does is declare: "That what is in the prime interest of a person who is seeking the best is in the performance or non‑performance of an act."
The Istikhara is the means from which one is saved from doubt and uncertainty. However, as for the after‑effects that will happen in the future by either performing or not performing the action, they are not the responsibility of the Istikhara, and the Istikhara has no relation to this.
The future of a person who performs the Istikhara ‑ whether it will be good or bad ‑ is just like the person who had not performed an Istikhara and carried on with his life using his own intellect and asking advice from others. In short, the Istikhara is nothing more than an act that provides "satisfaction of the heart," "removes doubt and uncertainty," and is a tool for "hope, prosperity and happiness."
From the authentic narrations related from both the Shi`a and the Ahl alSunnah, it has been mentioned that the Prophet of Islam s used to ask for the best and used to encourage those around him to do so. He forbid people to ridicule the Istikhara and said, "Any time the Istikhara comes out `bad', have reliance on Allah and go on with the work."
Therefore, there is no problem with performing an Istikhara by way of the Qur'an or other things, since if the Istikhara comes out favourable, then the person will perform the action with a content heart and a pure soul; and if it comes out bad, then he has relied upon Allah and should continue with his work."
`Allamah Shahid Murtada Mutahhari
"...What kind of talk is this that the `Ulama (only) must perform the Istikhara! How many problems this misconception has brought up! An `Alim is sitting in his house, busy studying or writing, the telephone rings and the person on the other end asks: `Sir! I am sorry to bother you, I need an Istikhara...'
Regardless, I myself perform Istikhara (for others), and I am not opposed to it, but it is better that each person performs an Istikhara for himself. Some people have even said that it is not allowed for a person to perform an Istikhara for someone else and everyone must perform it for himself!"
Ayatullah Shahid Husany Dastzhaib Shirazi
"Istikhara literally means to `ask the best' from Allah . O' Allah! I am perplexed and do not know if Your pleasure is in this task or not (which I wish to perform). I ask You to make apparent Your pleasure upon me.
However, in this state, it is necessary for one to supplicate to Allah (swt), and the true Istikhara is just this ‑ supplication. If by this method, one's confusion is not removed, then it is not a problem that to remove the doubt and uncertainty, then one acts according to that which has been mentioned in the narrations and by either the Tasbih or the Qur'an, he can seek to alleviate his difficulties.
However, two conditions must be fulfilled, the first is that the person must be in a state of supplication meaning that his state be such that he truly feels: `O' Allah! Please remove the doubt in me through the blessings of the Glorious Qur'an.'
The second condition, which is the most important one, is understanding the context and meaning of the verses of the holy Qur'an ‑ including the particularities in relation to an Istikhara.
It must be made known that the Qur'an was not revealed simply to perform the Istikhara. Rather, it is a book of knowledge and wisdom, which guides one to the paths of servitude of Allah . Don't get me wrong, I am not opposed to performing the Istikhara by the Qur'an, but those two conditions must be primarily fulfilled.
In the event that after thinking, supplicating and asking others for advice, one still remains in a state of doubt, then the best way to remove this uncertainty, which has also been mentioned in the narrations, is to perform an Istikhara, and that too by the method known as "Dhat al‑Raqa”  meaning the Istikhara using papers, which even the most well‑known Fuqaha' (Scholars) used to perform."
Ayatullah al‑`Uzma Shaykh Muhammad Taqi Behjat
"Regarding the instances in which one should perform an Istikhara ‑ after seeking advice from those people who are well informed and knowledgeable, if there still remains doubt, then and only then should one perform an Istikhara.
The various types and methods of Istikhara have been mentioned in Mafatih al‑Jinan and the various books of ahadith. As for the question that is anyone able to perform an Istikhara by the Qur'an or Tasbih beads for himself or not, it must be stated that if all the conditions and etiquette are followed, then it is not a problem."
Ayatullah al‑`Uzma Shaykh Nasir Makarim Shirazi
"There are numerous narrations relating to the Istikhara, and it in itself (the Istikhara) is something that is good to perform. Many successful results have been seen from it, as long as thinking and contemplation, and seeking the advice from others proves to be not enough for the person to make up his mind to perform or not to perform a certain task.
In such a situation of doubt, it is in place to perform an Istikhara. However, whatever the outcome may be, whether it is in accordance with one's wishes or against one's desires, it mast be accepted. Anytime, one performs an Istikhara by asking others for advice and help, one should accept that and must not proceed with the `traditional Istikhara', since it is clear that this was not a place to perform that Istikhara.
However in this type of a situation, it is better than after waiting some time, give some charity, and then carries on with the task.
We have mentioned the conditions for a proper Istikhara in writing and the people can refer to the book `Qawa'id al‑Fiqhiha' in the last discussion on `casting lots' for more information."
 Surah Naml (27) Verse 62
 Hadith 35 as found in this book