According to Bukhari, Volume 2, Book 21, Number 263:
Narrated Jabir bin 'Abdullah :The Prophet (Sallal Laho Alaihi Wasallam) used to teach us the way of doing Istikhara, 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 obligatory prayers, and then say (after the prayer):

Arabic:

Translation:

Oh Allah! I seek Your guidance by virtue of Your knowledge, and I seek ability by virtue of Your power, and I ask You of Your great bounty. You have power; I have none. And You know; I know not. You are the Knower of hidden things.

Oh Allah! If in Your knowledge, (this matter*) is good for my religion, my livelihood and my affairs, immediate and in the future, then ordain it for me, make it easy for me, and bless it for me. And if in Your knowledge, (this matter*) is bad for my religion, my livelihood and my affairs, immediate and in the future, then turn it away from me, and turn me away from it. And ordain for me the good wherever it may be, and make me content with it.

Transliteration:

Allahumma inni astakheeroka bi ilmik. Wa'astaq-diroka biqodratik. 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-amra*) khayul-lee fi deenee wama ashi wa ajila amri wa'ajilah, faqdorho lee, wayassirho lee, thomma-barik lee fih. Wa'in konta ta lamo anna (hathal-amra*) sharrul-lee fi deenee. Wama ashi. Wa ajila amri. Wa'ajilaho. Fasrifho annee. Wasrifnee anh. Waqdur leyal-khayr haytho kan. Thomma ardini bih.

One who seeks guidance from his Creator and puts his trust in Allah SWT does not regret, for Allah has said :

''...and consult them in the affair. Then when you have taken a decision, put your trust in Allaah.."(chapter 3 verse: 159)