I think most undergrads feel that LORs are out of their control and they just look for the professor they actually went to office hours for or something. However, I'd say it is one of the app factors you have the most control over since you can always choose who you interact with, how much effort you put in, building a relationship etc. Taking a class with a small number of people and working in a lab are probably the best ways to obtain a meaningful LOR and one that you may not even have to ask for. Two of my professors have told me after a semester on separate occasions "don't ask me for a LOR, just tell me where to send it" and those were both very small classes (~12 students). Meanwhile, a lot of my friends who only took the most trafficked (often because they are easier or major-sequence) courses are panicking now that they are in 2nd semester of third year and have no idea who to ask for letters.