The Arabic word Istikhara is from the root ‘khayr’ خير meaning goodness and it is form X verb which means seeking / investigating for that which is good. Although the word istekharah is not found in the book Quran nevertheless it is commonly to refer verse 2:153 in favor of “prayers of istekharah”
يَا أَيُّهَا الَّذِينَ آمَنُواْ اسْتَعِينُواْ بِالصَّبْرِ وَالصَّلاَةِ إِنَّ اللّهَ مَعَ الصَّابِرِينَ
2:153 - O you who have believed, seek help through patience and salah. Indeed, Allah is with the patient.
So, whenever we need to decide on an important issue, we must ask our own system of consciousness [Allah] for His help to guide us to the right choice. We must do this by patiently connecting (salat) with our own script [Al-Kitab] and asking our consciousness [Rabbana] for guidance to show us the choice that which will be good for us. Furthermore we should not forget the word istekharah [استخارة] means to investigate and look for good and righteousness.
Note: Salah is not ritual prayer. By offering ritual prayer you will get nothing except placebo effect. You are not dictating Allah through ritual prayers to show you a vision or through a dream what is good for you nevertheless you are fooling your own self.