For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I: Before the Island
Before landing on the island, Crusoe's father wants him to be a good, middle-class son. Crusoe, who wants nothing more than to travel the world in a ship, is definitely not into this idea. He struggles against the authority of both his father and God and decides to thumb his nose at both by going on a seafaring adventure instead.
After sailing around a while, he makes a bit of money in trade, but then gets captured and made into a slave off the coast of Africa. Here, he befriends a young man named Xury, with whom he escapes from captivity. Picked up by a Portuguese sailing captain, Crusoe makes it to Brazil, where he buys a sugar plantation. He does fairly well financially, but soon becomes involved in a venture to procure slaves from Africa. On the voyage out, he gets shipwrecked and is left as the only survivor on a deserted island.
Act II: Life on the Island
This portion of the novel is dedicated to Crusoe's time alone on the island. He builds three main structures: his initial shelter, his country home on the opposite side of the island, and his guns and ammo fort in the woods. He spends his time planting corn, barley, and rice. He learns to make bread. He builds furniture, weaves baskets, and makes pots. Crusoe also raises goats and tends to his little animal family of cats, dogs, and a parrot. Most importantly, though, Crusoe becomes stronger in his religious faith, eventually submitting to the authority of God. He devotes himself to much religious reflection and prayer.
Act III: Escape from the Island
In final section of the book, Crusoe sees a footprint on the shore one day and learns that he is not alone on the island. There are also (gasp!) cannibals. Crusoe struggles with the question of whether or not he should take revenge on them. Eventually, he meets with Friday, a native man whom he is able to rescue from the cannibals. Crusoe teaches Friday English and converts him to Christianity. The two become like father and son (more or less). Friday and Crusoe also rescue a Spaniard and Friday's father from a different group of cannibals.
Eventually, an English longboat full of sailors lands on the island. Crusoe learns that the men have mutinied against their captain. After Crusoe helps restore order to the ship, the men and captain pledge allegiance to Crusoe and agree to take him home. Crusoe then returns to Europe with Friday, where he comes into a great deal of money from his sugar plantations. Crusoe gets married and eventually revisits the island in his later years. The novel ends with promise of more adventures in the sequel.