The Beloved Messenger, sallallaahu 'alaihi wa sallam, taught us a method of consulting Allah Subhanahu wa Ta'ala in order to make major decisions. This is called Istikharah. The du'a of Istikharah can be found in many books of the du'as of Rasulullaah sallallaahu 'alaihi wa sallam. However before doing Istikharah one should be firm that he/she will strive to act according to the indications received.
The method that we have been taught is that before going to sleep, one should perform two Rak'aat Nafl and then say the du'a. When one reaches the statements "Oh Allah, if You know that this matter is good for me..." and "Oh Allah if You know that this matter is evil for me..." you should think of the "matter".
You should then go to sleep without talking to anyone. When you wake up, before doing anything, consider your inclination to this matter. Do this for a minimum of 3 consecutive nights, up to a maximum of 7 consecutive nights.
If you find that your inclination towards that matter increased over the days, you take this to mean that this is good for you. But if you find that your inclination decreased, then this is an indication that the matter is not good for you. Then you need to strive according to the indication you received from "consulting" Allah Subhanahu wa Ta'ala.
And Allah Ta'ala knows best!