How do I get recommendation letters? I have had a different set of professors every semester and as batch sizes are pretty big ~80, and with every professor dealing with 3-4 separate batches of equivalent size, for barely 3-4 months at a time, it has been hard to develop one to one relationships with professors. In such a scenario,


How do I decide whom to approach for a recommendation?
How should I go about this to get a good recommendation, in this specific scenario?
Given the OP’s situation explained in his question and the following comments that he has trouble with getting recommendation letters written by his professors themselves, if I were him I would


  
    Find the professor who would write the recommendation letter himself.
    
    Find the professor who taught the class which I had very good grade.
    
    Find the professor who taught the class in which I was most interested.
  


Usually, I need three recommendation letters. Now, I have three.

My personal experience is that I tend to have good grades when taking the class I am very interested. If I had good grade in a class I was interested, the chances are the professor would remember me and more willing to write the recommendation letter himself for me.