Basically, The Lord of The Rings is just an elaborate retelling of The Hobbit.
The first chapter in each work speaks for itself: "An Unexpected Party" versus "A Long-expected Party".
In both stories, a young hobbit leaves his home to brave the dangers of the outside world. His destination is a mountain, situated in a desolate place, filled with fire. He is taken care of by Elves in Rivendell. On his quest, he travels in a group mostly consisting of people not of his own race. The group travels with pack ponies, which it loses, twice.
The company meets partying elves in a forest. They leave the elves going down a river. The river leads to a city of men.
They enter a dark, scary network of caves through a hidden door. The mightiest creature in the caves is slain.
The hobbit miraculously survives a spider attack. While one part of the company is taken captive, the remaining hobbit and sneaks into the prison to the rescue, using a ring which makes him invisible.
Many times, he wishes he were back in his own safe world. He also proves that, despite a weak first impression, he's someone to be reckoned with.
The hobbit spends some time in Rivendell in order to heal and gather his strength after the adventure. When he finally returns, his home is not the way he left it, as Gandalf has warned him. The hobbit never settles down completely after his adventures, as he does not fit in the Shire anymore.