This virtue is the hardest one to improve because it needs to be worked to become a virtue, for wisdom is to have the ability to observe things and perception to understand them, so it is needed to develop a way to see the world with analytic eyes. Everybody can make wise decisions sometimes, but to be wise we have to live in wisdom and for this we have to really immerse ourselves in this virtue.
If we have knowledge and sense developed we can understand the world around us and how things and people are, so that we are able to comprehend the past in the current day, and looking to the future, apply this. This is wisdom.
The beginning is to learn about history, society and the whole of human existence, not only in books but also in experience and oral tradition, learned from our ancestors and wise men. When we mixed it with the perception to transcend it and understand the outlines behind the facts, we have wisdom.
So the knowledge is only the start, for all information is empty without a fertile mind analyzing and thinking about it, accumulating teachings and experiences, questioning and exploring until it transforms knowledge and sagacity into understanding. And only with the genuine understanding of things comes wisdom.
Therefore we can say that wisdom is to take the correct decisions and judgments based on the understanding of people and situations, keeping in mind that we are all part of a whole. A wise man must be conscious of why he is acting that specific way and not be unfair with himself or others, because he knows that everything is connected and the correct choice is always the consequence of the right perception of truth.