"I want to attempt a thing like that and am frightened by these trifles," [Raskolnikov] thought, with an odd smile. (1.1.5)
This is the first time we hear about Raskolnikov's bad idea. Even though most people already know the book is about a murder before they read it, it's still creepy and mysterious.
[Raskolnikov] was positively going now for a "rehearsal" of his project, and at every step his excitement grew more and more violent. (1.1.9)
Uh-oh. He really sounds like a criminal here. Depending on the crime, rehearsing can get you into almost as much trouble as actually committing it.
[Marmeladov:] "She walked straight up to Katerina Ivanovna and she laid thirty roubles on the table before her in silence." (1.1.21)
This is how Marmeladov describes Sonia's return from her first prostitution job. Though prostitution wasn't illegal in Russia during this time, Katerina and Marmeladov are committing a moral crime against Sonia by forcing her to do it.
Part 1, Chapter 4
Rodion Romanovitch Raskolnikov
"Hey! You Svidrigaïlov! What do you want here?" [Raskolnikov] shouted, clenching his fists and laughing, spluttering with rage. (1.4.14)
Raskolnikov (and the readers) have only heard about Svidrigaïlov by this time. Raskolnikov calling the sketchy man in the park "Svidrigaïlov" foreshadows his presence in St. Petersburg and prepares us for his nastiness.
Part 1, Chapter 6
"Kill her, take her money and with the help of it devote oneself to the service of humanity and the good of all. What do you think, would not one tiny crime be wiped out by thousands of good deeds?" (1.6.14)
This isn't Raskolnikov talking but rather another student. The passage simply states the complicated question posed over and over in the novel. What do you think? Can killing ever be justified? If so, when and why? If not, why not?
Part 1, Chapter 7
Fear gained more and more mastery over him, especially after this second, quite unexpected murder. (1.7.28)
We wonder how this book would have turned out if Raskolnikov hadn't killed Lizaveta. Since Raskolnikov is partially inspired by his desire to protect Lizaveta from Alyona's beatings, it's extremely ironic that he ends up killing her, too.
Part 3, Chapter 5
Rodion Romanovitch Raskolnikov
[Raskolnikov:] "I […] hinted that an 'extraordinary' man has the right […] an inner right to decide in his own conscience to overstep...certain obstacles, and only in case it is essential for the practical fulfillment of his idea (sometimes, perhaps, of benefit to the whole of humanity)." (3.5.101)
This is a more complicated-sounding version of what Raskolnikov hears the student say in the quote above from 1.6.14. This is when he's trying to explain his article on the matter to Porfiry. Knowing that he wrote an essay about this business helps us understand just how obsessed he really is with the idea.
Part 4, Chapter 4
All that infamy had obviously only touched her mechanically, not one drop of real depravity had penetrated to [Sonia's] heart; [Raskolnikov] saw that. (4.4.104)
Not only does Raskolnikov assume that Sonia does her work in a machine-like way, with no feeling, he implies that prostitution, something one does with one's own body, can actually have an impact on the "heart," by which he really means "soul." A moment later, he suggests that, if she stays a prostitute, she will go crazy, kill herself, or start to enjoy it. In other words, if she keeps it up, she'll lose her soul. He sees her as a criminal, even though she doesn't see him as one.