What are some significant actions made by the characters in A Raisin in the Sun?

This is a big question, but I'll try to give a few of the major actions that characters take in the story. Many of the family's actions are taken as an attempt to better their lives, so I'll start there. Lena, the matriarch of the family, makes the choice to use at least part of her $10,000 insurance check from her husband's death to put a down payment on a nice house in a white neighborhood, fulfilling the dream of upward mobility that she and her husband had for their family. Walter takes another significant action by disobeying his mother; instead of splitting the rest of her check between himself and his sister Beneatha, he spends it all on a business plan he has been working on with two other men. While Lena sees success for the family through a nice new house, Walter sees it through going into business for himself and making money for the family. The different characters' views of success and happiness cause most of the conflict in the plan, especially when it comes to the fate of the $10,000 (and when Walter's partner runs off with the rest of the money).

Another important action is taken for the opposite reason: because the family doesn't have enough money to support another child, Ruth decides to get an abortion when she finds out she is pregnant again. Though her intentions are good, Lena is horrified by the decision and Walter's feelings of being an inadequate husband and provider are exacerbated. 

Finally, Walter makes two more major decisions and actions in the play that drive the plot. First, he accepts the offer of Karl Linder, who wants to buy the house Lena just put a down payment on in order to keep the neighborhood white only. Again, Walter is choosing money over his mother's measure of success and happiness. In the end though, Walter rejects the offer and the play ends with the family leaving their little apartment for the final time.