The Dua Istikhara is a prayer for guidance. The dua, supplication, Al Istikhaara is recited, after 2 rakahs of prayer or during the tashahhud of the 2 rakahs. The translation of the supplication is as follows:
اللَّهُمَّ إِنِّي أَسْتَخِيرُكَ بِعِلْمِكَ وَأَسْتَقْدِرُكَ بِقُدْرَتِكَ وَأَسْأَلُكَ مِنْ فَضْلِكَ الْعَظِيمِ فَإِنَّكَ تَقْدِرُ وَلَا أَقْدِرُ وَتَعْلَمُ وَلَا أَعْلَمُ وَأَنْتَ عَلَّامُ الْغُيُوبِ اللَّهُمَّ إِنْ كُنْتَ تَعْلَمُ أَنَّ هَذَا الْأَمْرَ خَيْرٌ لِي فِي دِينِي وَمَعَاشِي وَعَاقِبَةِ أَمْرِي فَاقْدُرْهُ لِي وَيَسِّرْهُ لِي ثُمَّ بَارِكْ لِي فِيهِ وَإِنْ كُنْتَ تَعْلَمُ أَنَّ هَذَا الْأَمْرَ شَرٌّ فِي دِينِي وَمَعَاشِي وَعَاقِبَةِ أَمْرِي فَاصْرِفْهُ عَنِّي وَاصْرِفْنِي عَنْهُ وَاقْدُرْ لِيَ الْخَيْرَ حَيْثُ كَانَ ثُمَّ ارْضِنِي بِهِ
"Allahumma inni astakheeroka bi ilmik (2)
Wa'astaqu-diroka biqodratik (2)
Wa'as'aloka min fadlikal-azeem.
Fa'innaka taqdiru wala aqdir. Wata lamo wala-a lam, Wa'anta-allamul ghuyoob.
Allahumma in kunta ta lamu anna hathal-amr
(Here You Mention Your Need)
Khayul-lee fi deenee wama ashi wa akibiti amri (Repeat Entire Paragraph 2 Times).
Faqdorho lee, wayassirho lee (2) Thomma-barik lee fih.
Wa'in konta ta lamo anna hathal-amr, Sharrul-lee fi deenee Wama ashi Wa akibity amri.
Fasrifhu annee. Wasrifnee anh.
Waqdur le-yal-khayra haytho kaan (3) Thomma ardini bih."
'"O Allah, I ask You to show me what is best, through Your knowledge, and I ask You to empower me, through Your power, and I beg You to grant me Your tremendous favor, for You have power, while I am without power, and You have knowledge, while I am without knowledge, and You are the One who knows all things invisible. O Allah, if You know that this undertaking(or insert the specifics here in place of undertaking) is in the best interests of my religion, my life in this world, and my life in the Hereafter, then make it possible for me and make it easy for me, and then bless me in it. And if You know that this undertaking(or insert the specifics here in place of undertaking) is not in the best interests of my religion, my life in this world, and my life in the Hereafter, then keep it away from me and keep me away from it and choose what is good for me wherever it is and make me content with it."
Those seeking guidance are advised to repeat this prayer, as many times as needed. Some scholars hold that the prayer will be answered with a dream, or by elements of a dream. However, the majority opinion is that the unfolding of events will naturally reveal the answer to the prayer. For example, if this prayer is made in order to seek guidance as to whether one should travel abroad or not, the fact after the prayer that all flights were booked (or any other situation which would make traveling abroad very difficult) is in fact thought to be the answer to the prayer, telling one that it was in one's best interest not to go. If instead, it was found that the travel plans went very smoothly, that instead would be interpreted as the answer to the prayer, telling one that it was in one's best interests. Some hold that one would simply have a feeling that would urge one to make the correct choice.
For Shias, there is also an Istikhara using the Quran. This is similar to an ancient practice in Judaism where the Holy Book is used as a guide in the practice of your free will in decisions. For Shias, the Istikhara is usually performed by an alim and a prayer is said before the Book is opened for interpretation.