Signs can be in the form of good dreams wherin a person is shown whether or not the matter is good for him. The dream directly or indirectly indicates the path that should be taken. It is advisable to have the dream interpreted by a pious man who has the knowledge and experience of interpreting dreams, because it is likely that a normal person would misunderstand his dream.
However, it is not neccessary to see a dream. Many a time the answer is just understood in the form of a strong feeling. When performing Istikhaarah we ask Allaah to decree the matter in question for us, if it is good for us, and turn it away if it is not. Hence, whatever confusion you may experience prior to performing Istikhaarah is generally removed, and you feel more focused. Take notice of what your heart feels inclined towards after performing Istikhaarah. That is your answer.
It is best to perform Istikhaarah for 7 consecutive days. If you still do not get an answer, continue for another 7. If after 14 days, you still feel unsure, you may continue upto 21 days.
If one still sees no signs, then have faith that whichever of the two options naturally took its course, was the best for you. As you have asked Allaah to ease the way for the matter to materialise if it is good, and turn it away if it not. If Allaah creates obstacles in the way to making that matter take place, then see it as a sign that it was not good for you. On the other hand if any obstacle that was there prior to istikhaarah was somehow removed, then consider it to be a sign that it is good for you.