Istikhara after a two Rak`at Mustahab Salat
Imam al‑Jawad (as) aid: `It is best that you seek the best (from Allah) after a two rakat Salat. " 
Istikhara after Salat
Imam al‑Sadiq (as), said: `If any of you wish to do something, (then start off by) praying a two rak`at Salat and praise and extol Allah and send blessings on the Prophet and his family then say:
O' Allah if there is good in this action for me in my religion and in my life, then make it easy for me and destine it for me; but if it is other than this, then turn it away from me. " 
Istikhara after Salat al‑Fajr
Imam Jafar al‑Sadiq (as) said: "When you have finished Salat al‑Fajr, then lift up your hands such that they are in front of your face and say the following:
O' Allah, verily You know (better) and we do not know and you are the Knower of the Unseen, so send blessings on Muhammad and the family of Muhammad and give me the best in all that I resolve to do of that which will be a blessing and good (for me).
Then go into sajdah and say the following line one hundred times:
I ask the best from Allah by Your Mercy, and I seek the power and strength to perform this good work from Allah. "
Then, ask for your (legitimate) desires since in this is what is good for you in whatever happens."
Istikhara in the Final Sajdah of Salat al‑Lail
al‑Imam al‑Sadiq (as) said: "In your final rakat of Salat al‑Lail, while you are in sajdah, ask Allah for the best by reciting the following one hundred and one times:
`I seek the best from Allah by His mercy. " 
Istikhara in the Final Sajdah of Nafilah of Salat al‑Fajr
Imam al‑Sadiq (as) said the following regarding asking Allah for the best: "In the final sajdah of the recommended prayers of Salat al‑Fair, one should seek the best from Allah by praising Allah and sending blessings on the Prophet and his family and then by asking Allah for the best fifty times followed by praising Allah and sending blessings on the Prophet one hundred and one times. " 
 Fath al‑Abwab, Page 143 / Wasa'il ash‑Shi'a, Volume 8, Page 77, Hadith 10122
 Man La Yahduru al‑Faqihi, Volume 1, Page 355, Hadith 1554 / Tahdhib alAhkam, Volume 3, Page 180 / Wasa'il ash‑Shi'a, Volume 8, Page 66, Hadith 10099
 Makarim al‑Akhlaq, Page 320 /Man La Yahdhuru al‑Faqihi, Volume 1, Page 355, Hadith 1555
 Wasa'il ash‑Shia, Volume 8, Page 73, Hadith 10112 / Man La Yahdhuru al‑Faqih, Volume 1, Page 355, Hadith 1556