Ask HN: How to best read source code

One of the limitations I face when I want to contribute to open source projects is the difficulty I associate with navigating and reading code. Is there a way I can follow code so that it can make sense to me, a novice programmer? The best way I think is to follow the chronological order of code commits, so that I follow what the developer had in mind. Problem is, most developers push a large portion of their code base at once,which makes my trick obsolete.