I am currently thinking about getting a masters degree and many of the schools I look for require 3 reference letters from professors that has taught me.
Unfortunately, I've never really invested in building personal relationships with my professors and though I am quite confident with my ability, my abilities weren't "amazing" to the point where the professor would notice me personally.
Furthermore, I've already graduated and worked for more than a year, hence I don't believe any of my previous professors retain much memory of me.
In such a situation, how would I go about getting 1 (let alone multiple) reference letters from previous professors?