Was going to simply walk into Mordor, until he took three arrows to his chest.
Although having the best intentions to use the Ring to aid Gondor in the struggle against Sauron and the armies of Mordor, He didnt realize that the Ring would corrput all who desired it.
Boromir assaulted Frodo in the woods of Amon Hen for possession of the Ring, but soon thereafter realized his geat-mistake. Boromir then redeemed himself by fending off hordes of Orcs to save Merry and Pippin, but was eventually killed, and Merry and Pippin kidnapped.
He was a member of the fellowship, until Lurtz killed him. Because he tried to take the one ring, many people believe him to be one of the 'bad' characters, and he is often portrayed as the chauvanist or sarcastic jerk in fanfiction.
The truth is that he was used by Tolkien to show that anyone, even those with the best of intentions, or the strongest of wills, could be seduced by the ring's power.
And no matter what anyone says, even if they say what he did was dishonorable, he redeemed himself in the end by sacrificing himself to try and save Merry and Pippin.