I got this from archive posts. Kinda long but very useful :
This is the way of istikhaarah. This is the way to get the message from Allah - and you can then plan accordingly. And proceed with tawakkal (trust) in Allah Ta’ala, for in this way your life will be filled with blessings. Rasoolullah used to do istikhaarah himself, and the Sahaabah also used to do it. How beautiful it is to have confidence in every step of your life.
Sometimes, often in respect of marriage, your parents try to force you to do something. You make istikhaarah and it gives different guidance from that of your parents - but they don’t want to listen. This is very harmful, for if a person goes against istikhaarah, having taken advice from Allah and knowing that it is right, then only loss can be expected to follow. I have witnessed such things. One person whom I knew some twenty years ago when I was a student, was a doctor and he wanted to come for further studies to London. His mother said make istikhaarah. I was about twenty five years old at the time. So he did istikhaarah and saw that it was not good for him to travel to London for further studies. He told his mother, but because they wanted to send him to London, they said it was alright for him to go - and the whole family persuaded him to go. So he bought the ticket for London. When the aeroplane came in to land at the airport it crashed, and himself and the other passengers inside the plane all died instantly. The relatives of the man knew that what they had done was wrong.
When you consult Allah, then there is no need to worry. Even if it appears bad, the result will be good. It increases the confidence of a person and removes doubts. Don’t listen to any other sources after you have sought guidance from Allah. We constantly have problems and decisions before us, and istikhaarah is the best way to resolve these matters. May Allah bless you and me, and I hope and pray that we follow the life of Nabi Kareem in every way. Istikhaarah was the habit of Rasoolullah, and he told us to do it when we have decisions to make in our lives. May Allah Ta’ala bless you and me. (Ameen)
I made once an istakhara because there was a college in another town ready to accept me and I wasn't sure about it until I made this istakhara. I felt good about it and everything went fine. Before I applied we had to go to the town itself to check if environment is suitable. When I got there, I really disliked it and didn't feel good about staying there so I changed my mind.
After few months we heard from the news that problems were starting to erupt in that area and the place became unsafe.
Then dad said I was lucky that I didn't apply and get there. And for me it was strange because the istakhara went fine...I guess. Or maybe I didn't perform the istakhara right? You just perform two rakaats (how do you say it?) at anytime. Is it mandatory to say a duaa after it?
And I don't know how you can really tell if you're positive with it or not.
I know this topic has been opened many times in this forum but I think I don't understand it well still.
By the way I rarely perform it.
Don't get me wrong please.