There are many lessons that Santiago learns in Paulo Coelho's The Alchemist. Truthfully, I find something new each time I pick the book up again. One of the beautiful things about this short novel is that the simplistic story is overflowing with meaningful pieces of wisdom (life-lessons).
Santiago learns that things are not always as they appear. For instance, he thinks his recurring dream is a promise of money; actually it is a promise of personal achievement, and hopes and dreams realized. He believes that the young man who befriends him in the market place is actually trying to help him, but Santiago learns that the man was only interested in stealing his money.
Santiago learns that the world around him is speaking to him through omens all the time. One of the most impressive omens that Santiago recognizes is that of the hawks fighting: the vision that comes to him reveals that the oasis will be attacked, and he is able (through his warning) to save lives.
Santiago learns that sometimes a negative thing can really be a blessing in disguise. When he is robbed, he is tempted to give up the pursuit of his Personal Legend. When he is forced to work for the crystal merchant, he must learn patience. He finds satisfaction in what he does, but helps the merchant as well. The "boy" also learns important lessons from the life experiences of the crystal merchant—things that convince him to continue.
From the Englishman, Santiago discovers that he cannot be what he is not: this includes trying to think like the Englishman. Santiago's companion (while crossing the desert) believes that knowledge comes from books. Santiago considers this and even tries to learn this way, but he soon finds that books do not speak to him: the world does, through omens and the Language of the Universe.
There are many other things Santiago learns, but perhaps the most important lesson is that life's rewards sometimes present themselves in surprising or unexpected ways. Some of the things that become the most valuable to Santiago are finding love with Fatima, becoming one with the universe and connecting with the Soul of the World. He finds surprising riches on his journey to find himself.