The Bark Bites Back at 2012-12-18 18:36:01:
Structure wise, it follows three acts fairly close. The first act turn appears to be George's father's death and his decision to stay. The second act turn is George on the bridge and his visit from Clarence.
It's interesting to see each decision is marked by what is arguably what is one of the central themes regarding greed/selfishness vs. selflessness. Every time George is in a position to do something for himself, extenuated by temptation from Potter, he's forced to look at who he is and finds the answer in an act of selflessness.
Early on, in the dinner scene with his family, his father tells him no - move on and get out of Bedford Falls. Just when George thinks he's getting his wish, he's forced to choose between a selfish desire to escape and the selfless to stay.
This plays nicely into the later scene with him contemplating suicide, believing everybody else would be better off without him. We all know suicide is a selfish act and once again George is tempted by Potter who has called the cops on him (earlier, he's tried to tempt him with a position and salary).
Whereas George is often tempted to do something selfish to acquire what he wants, he always takes the selfless road - whether it's dancing with somebody's kid sister and eventually marrying her despite his desire to leave, using his honeymoon money to stop a crisis, or loaning money for an old friend to find her own way out, these are all selfless acts that counter the greed and manipulation of Potter.
In the end, it's the town who rewards George in their own act of selflessness by coming to his aid and bailing him out.
I know some of this touches upon thematic elements, but it's hard not to discuss them when they are in fact part of the story's structure (or in this case, the apparent argument the story is making with regards to values and morals vs. greed).