What is the correct way of doing istikharah? I have found a lot of different methods online but not sure which one is authenticated.
Narrated Jabir bin 'Abdullah :
The Prophet (Peace be upon him) used to teach us the way of doing Istikhara (Istikhara means to ask Allah to guide one to the right sort of action concerning any job or a deed), in all matters as he taught us the Suras of the Quran. He said, "If anyone of you thinks of doing any job he should offer a two Rakat prayer other than the compulsory ones and say (after the prayer): -- 'Allahumma inni astakhiruka bi'ilmika, Wa astaqdiruka bi-qudratika, Wa as'alaka min fadlika al-'azlm Fa-innaka taqdiru Wala aqdiru, Wa ta'lamu Wala a'lamu, Wa anta 'allamu l-ghuyub. Allahumma, in kunta ta'lam anna hadha-l-amra Khairun li fi dini wa ma'ashi wa'aqibati amri (or 'ajili amri wa'ajilihi) Faqdirhu wa yas-sirhu li thumma barik li Fihi, Wa in kunta ta'lamu anna hadha-lamra shar-run li fi dini wa ma'ashi wa'aqibati amri (or fi'ajili amri wa ajilihi) Fasrifhu anni was-rifni anhu. Waqdir li al-khaira haithu kana Thumma ardini bihi.' (O Allah! I ask guidance from Your knowledge, And Power from Your Might and I ask for Your great blessings. You are capable and I am not. You know and I do not and You know the unseen. O Allah! If You know that this job is good for my religion and my subsistence and in my Hereafter--(or said: If it is better for my present and later needs)--Then You ordain it for me and make it easy for me to get, And then bless me in it, and if You know that this job is harmful to me In my religion and subsistence and in the Hereafter--(or said: If it is worse for my present and later needs)--Then keep it away from me and let me be away from it. And ordain for me whatever is good for me, And make me satisfied with it). The Prophet added that then the person should name (mention) his need. (https://muflihun.com/bukhari/21/263)
Istikhaarah is a two rakah Sunnah. The Du'a which is to be recited before (or after) the Salah is marked with bold letters in the above Hadith.
There are three opinions as to what should be recited in Salaat al-Istikhaarah:
(a)The Hanafis, Maalikis and Shaafa’is said that it is mustahabb, after reciting al-Faatihah, to recite Qul yaa ayyuha’l-kaafiroon in the first rak’ah and Qul huwa Allaahu ahad in the second. Al-Nawawi said, explaining the reason for that: It is appropriate to recite these in prayer, to show sincerity and expressing your leaving your affairs to Allaah. They said that it is also permissible to add other verses from Qur’aan where the context refers to the idea of making a choice or decision.
(b)Some of the Salaf said that in praying istikhaarah it is good to add, after reciting al-Faatihah, the following verses in the first rak’ah:
“And your Lord creates whatsoever He wills and chooses, no choice have they (in any matter). Glorified is Allaah, and exalted above all that they associate (as partners with Him).
And your Lord knows what their breasts conceal, and what they reveal.
And He is Allaah; Laa ilaaha illa Huwa (none has the right to be worshipped but He), all praises and thanks be to Him (both) in the first (i.e. in this world) and in the last (i.e. in the Hereafter). And for Him is the Decision, and to Him shall you (all) be returned”
[al-Qasas 28:68 – interpretation of the meaning]
And the following verse in the second rak’ah:
“It is not for a believer, man or woman, when Allaah and His Messenger have decreed a matter that they should have any option in their decision. And whoever disobeys Allaah and His Messenger, he has indeed strayed into a plain error”
[al-Ahzaab 33:36 – interpretation of the meaning]
(c)The Hanbalis and some of the fuqaha’ did not say that any particular verses are to be recited when praying Istikhaarah. (https://islamqa.info/en/answers/11981/istikhaarah-prayer)
Note: The phrases used are "mustahab", "it is good to add", "did not say that any particular verses are to be recited". None of the three opinions says that you must recite this surah or that surah. From this, it is to deduce that no Surah (except Surah Fatiha) is fixed for Istikhaarah.
I hope you got the answer.