Istikhara is done to seek Allahu ta’ala’s guidance when one is unsure about a decision. It consists of performing wudu and Salat al-Istikhara, reading the relevant prayer, and sleeping in order to have a dream about a specific issue, in order to understand whether that issue is good or bad for oneself.

Hadrat Imam-i Ghazali states:

A person that performs four things will not be deprived of four things:
1. The one who gives thanks to Allahu ta’ala will not be deprived of an increase in blessings,
2. The one who repents will not be deprived of its acceptance,
3. The one who performs istikhara will not be deprived of auspiciousness,
4. The one who consults will not be deprived of finding the truth and reaching the reality.

One should perform istikhara before making decisions about issues, such as marriage or buying a house. It is stated in a hadith-i sharif:

(Happiness is realized by performing Salat al-Istikhara.) [Hakim]

Istikhara should be repeated several times before getting married, and one should seek refuge in Allahu ta’ala. One should pray that the nafs and bad people do not intervene in the decision. Istikhara should be performed after consulting with trustworthy and pious (salih) Muslims.

When someone wants to start something or get rid of something, he/she performs a voluntary (nafl) salat that consists of two rak'ats and reads the Arabic prayer mentioned below. Then he/she says, “If this thing [for instance, marrying someone or buying a house] is good for my life and afterlife, bless me with it. If it is not good for me, take it away from me and make the good choice easier for me. O the Most Merciful of the Merciful, make me among the ones who consent to Your qada'.”

One should first ask for forgiveness for all one's sins. In order to make repentance, one should briefly say, “O my Rabb, I am regretful for all sins I have committed since my puberty. I promise not to commit any sins from now on insha-Allah.” Then he/she performs ghusl. After ghusl, one prays a salat of two rak'ats that night after saying "I intend to perform Salat al-Istikhara." In the first rak'at, Surat al-Kafirun is recited after thana' and Surat al-Fatiha. In the second rak'at, Surat al-Ikhlas is recited after Surat al-Fatiha. The following prayer should be said after Salat al-Istikhara:

Allahumma innee astakhiruka bi-ilmika wa astaqdirüka bi-qudratika wa as’aluka min fadlikal azeem fa innaka taqdiru wa laa aqdiru wa ta’lamu wa laa a’lamu wa anta allaamul-ghuyoob.

Istikhara should be repeated for seven nights. [It is permissible to perform istikhara during the daytime.] Ghusl is performed only on the first day. Ghusl is not necessary on other days.

Istikhara cannot be performed for another person. Everybody has to perform it for himself or herself. Everyone needs to learn how to perform istikhara and perform this sunnat on his/her own. It is not permissible to have a person perform deeds performed with body in place of someone else.

One should sleep after performing Salat al-Istikhara without talking. He/she can talk to someone if it is necessary. Indeed, it is always mustahab not to talk unnecessarily after performing Salat al-Isha.

After Salat al-Istikhara, one gets into bed by turning toward the direction of qibla in a state of wudu'. Istikhara is continued for seven days, whether one has a dream or not. Seeing white and green colors in the dream augurs to goodness, while seeing black and red colors augurs to evil. If nothing is seen in the dream, one checks his/her heart. If there is a desire to do that thing, it is decided to be done. The person who cannot reach a decision should repeat istikhara several times.

It is sunnat and blessed to perform istikhara before every decision. But it is not necessary to see any evidence in the dream or while being awake for doing or not doing that thing. One should check his/her heart after the istikhara. If the desire to do that thing is more than before, he/she should to do that thing. If the desire to do that thing is the same as before, it is not forbidden to do that thing either. In that case, one should repeat istikhara until the desire to do that thing increases. If the desire to do that thing is less than before, he/she should not to do that thing. Istikhara can be repeated in that case as well. Whatever the situation is, it is always better to repeat istikhara. That provides caution in doing or not doing something.