Developing a strong relationship with professors provides a ton of opportunities with no real downsides. Here, we'll discuss many ways to gain a relationship with a professor.
Attending office hours not only gives you good information about the course material, it also allows you to connect more with a professor. If your prof is a lecture professor, that just means it'll matter even more, as most professors who teach lectures have hundreds of students in each class, so they likely won't remember you. However, most professors will remember students who consistently show interest in the material and learning. Show up once a week/every other week, and stay behind lectures to talk to professors.
Show up 5 minutes early. This is good life advice, but it will be especially helpful with professors. This is because most students come in at the last moment. By going in just 5 minutes early, you make the professor accustomed to you and will be more likely to strike up a conversation. You should also ask questions, answer questions, and be an active member in discussions. Basically, while you're in class, you just need to be present in mind and body.
When I say give a crap, I mean care about your peers and profs. If your prof tells you anything personal or something about their life, just take note. Talk to them in a professional manner, and check up on them. Professors are people too, and if you're in their office hours, then ask some more personal questions. Also, take care of your classmates. You might think professors don't notice this stuff, but when you help classmates in and outside of class, they will notice. It shows a lot of integrity on your side.
This is clearly the most obvious. If you don't do the work, it doesn't really matter how much you know your prof; they won't go to bat for a student with poor grades. B and above should be your target range, and for easier and general ed classes an A should be fairly easy.