Sam Gamgee is essential the anchor that Frodo can lean on during the course of the book. Sam is the motivator and is actually quite selfless. Sure, Sam is doing this partly for himself, but also for the whole shire. Sam knows that unless the ring is destroyed his comfortable little world is going to disappear. He’s very resourceful partly because he is a gardener. He recognizes useful plants as food. Several times in Mordor he is the one gathering water, though there were a few times they had to drink the unfit water there. Sam is determined. What is really neat is the contrast between Sam and Frodo. Sam is not influenced directly by the ring, while Frodo is. Frodo is being slowly consumed by the ring, while Sam remains mostly untouched. Watch how there mannerisms change throughout. I hope this helps.

There are excellent things mentioned here (except for the poster directly above me…..dude, read the book, Frodo NEVER told sam to leave and the only time sam ever left his master was when he believed him to have been killed by shelob).

What I would like to add is that because of sam’s “plain hobbit sense” he was able to resist the power of the ring even after he possed it. He is one of three characters who ever possed the ring and let it go willingly. (The other two, of course, being Bilbo and Tom Bombadil). I think this strength and his ultimate love for Frodo was incredibly crucial to the completion of their quest. I hope this helps.

being an honest and true friend to frodo. even during the time that frodo told him to go back to the shire, he still go back to rescue frodo when he find out that golum tricked frodo to distrust him by throwing the lambass bread..