Queen,
When mutual friends of the dating couple (same age) decide that it would be a good idea to fix up Chaim and Sara. Often these friends are room mates or in the same shiur with them.
Back in my day it was common for girls in the dorm at Stern to fix up a fellow dorm mate with a guy at YU. The contact was usually between siblings or close cousins at the 2 schools, so the boy girl contact wasn’t unusual or improper.
Sometimes, by the time room mates have spent a couple of years living together, they have a better idea what might make a good match than a shadchan.
In those days parents didn’t demand resumes and didn’t have 100+ item checklists (demands). My eldest son is already married almost 30 years. My daughter getting married I”H this Sunday met her chusan in Law School. They were the 2 always being seated together at school functions and being served airline meals. After the second semester, a female Jewish professor strongly suggested they consider marriage, that neither one would be happy with a spouse without advanced secular education.