[Boromir88]

Very nice and interesting questions Feredir.

Gandalf hints that the Ring has a will of it's own, and as Tolkien mentions in several places that the Ring does exude it's own lust, it's own 'pull.' I don't think I can explain the corruption of the Ring any better than Gandalf:

'No!' cried Gandalf, springing to his feet. 'With that power I should have power too great and terrible. And over me the Ring would gain a power still greater and more deadly.' His eyes flashed and his face was lit as by a fire within. 'Do not tempt me! For I do not wish to become like the Dark Lord himself. Yet the way of the Ring to my heart is by pity, pity for weakness and the desire of strength to do good. Do not tempt me! I dare not take it, not even to keep it safe, unused. The wish to wield it would be too great for my strength. I shall have such need of it. Great perils lie before me.'~The Shadow of the Past

The Ring uses the weaknesses of the individual against him/her. Boromir and Denethor both wanted to see the victory of Gondor over Sauron, arguably more than anything else, so the Ring appeals to them as a weapon that can be used to defeat Sauron. As Boromir (in his attempt to take the Ring from Frodo) speaks about armies flocking to his banner, and 'great victories.'

Sam, is a gardener, he loves it, and so when he is faced with the temptation of the Ring...

Already the Ring tempted him, gnawing at his will and reason. Wild fantasies arose in his mind; and he saw Samwise the Strong, Hero of the Age, striding with a flaming sword across the darkened land, and armies flocking to his call as he marched to the overthrow of Barad-dur. And then all the clouds rolled away, and the white sun shone, and at his command the vale of Gorgoroth became a garden of flowers and trees and brough forth fruit. He had only to put on the Ring and claim it for his own, and all this could be.~The Tower of Cirith Ungol

The Ring appeals to the desires of the individual. But, even though the Ring does have this natural 'lust,' whether someone 'passes the test' (to steal some words from Galadriel ) has as much to do with the individual, as the Ring is not 'all-corrupting.'

Let's take Gollum and Faramir for instance. Gollum immediately falls to the temptation of the Ring, and even murders to get it. Sam on the other hand resisted the Ring and even gave it back to Frodo.

In his Letters Tolkien wrote that Gollum was 'mean-spirited' and the 'mean son of a thief' and also:

'The domination of the Ring was much too strong for the mean soul of Smeagol. But he would never had to endure it if he had not become a mean sort of thief before it crossed his path.'~Letter 181

Despite the ring being too strong for Smeagol to over come, Tolkien also points out that his easy fall to the Ring has just as much to do with the type of person Smeagol was even before coming across the Ring.

Than we have someone like Faramir, who rejects the Ring right from the start, because as he tells Frodo:

'But fear no more! I would not take this thing, if it lay by the highway. Not were Minas Tirith falling in ruin and I alone could save her, so, using the weapon of the Dark Lord for her good and my glory. No, I do not wish for such triumphs, Frodo son of Drogo.'~The Window on the West

Faramir understood the Ring quite well. He knew that using it as a weapon against Sauron would only, in the end, benefit Sauron. So, Faramir was able to flat out reject the Ring, where Smeagol could not. Not only does this show Faramir being much stronger than Smeagol, but he simply knew the Ring was deceiving; as Smeagol believed he was entitled to the Ring, because it was his 'birthday.'

Hopefully that mostly provides the answers to what you were looking for.