Netherfield, rented by Mr. Bingley, Rosings, owned by Lady Catherine de Bourgh, and Pemberley, owned by Mr. Darcy, are each central to the plot development and the character development of Austen's story. Though several things happen at each place, it is not possible to give a full analysis here, but the start I can give will guide you on your way.
At Netherfield, Elizabeth stays to comfort and care for Jane after Mrs. Bennet's plan works too well and Jane develops a dangerous cold. While Elizabeth is there, the characters of the Bingley party are developed and given time to interact with Elizabeth. Jane interacts with Bingley in a quiet way as they tuck themselves in a quiet corner and talk unobserved, and, though unobtrusive, this is an important turning point for the romance between Jane and Bingley. Elizabeth experiences an equally important turning point with Mr. Darcy: he turns toward her "fine eyes" while she turns further away from him, though they establish a witty repartee and ease of conversation that is important later at Rosings. Also, remember the ball at Netherfield and what happens there relating to at least six key characters: at least Elizabeth, Darcy, Jane, Bingley, Collins, Wickham.
At Rosings, among many important events, Elizabeth has unexpected time to engage with Darcy in further conversation while he has ample time to observe her inner qualities and conversation with several other characters including Colonel Fitzwilliam. The most dramatic event that occurs at Rosings is Darcy's ill-stated, ungracious, though ardent marriage proposal to Elizabeth, her candid refusal of his proposal, and his brilliantly eloquent and heartrending letter of explanation (this is for some one of the most brilliant bits of reading in all English Literature). Remember also Elizabeth's conversations with Charlotte (who is not an insignificant character) and her private conversation with Fitzwilliam.
At Pemberley, the extremely important event of Elizabeth's re-encounter with Darcy occurs. None knew he would ride in that day--he was expected the next--and a face-to-face encounter was the last thing Elizabeth anticipated or wanted yet the one thing calculated to make her heart glad and hopeful. This encounter reveals profoundly important information about Darcy's character development (and Elizabeth's), showing his repentance and change of heart and his much mended manners. It also leads to an introduction to Miss Georgiana Darcy and to further encounters with the Bingley party thus juxtaposing sincere manners and affection with artificial manners and the absence of affection. Remember also the repair made to mistaken notions engaged by Bingley and the news from Jane about Lydia's infamy.
She burst into tears ... and for a few minutes could not speak another word. Darcy, in wretched suspense, could only say something indistinctly of his concern, and observe her in compassionate silence. At length, she spoke again. "I have just had a letter from Jane, with such dreadful news. It cannot be concealed from any one. My youngest sister has left all her friends -- has eloped;..."(Chapter IV, Volume III or Chapter 46)