If you want to overclock your PC, you're going to need to care a lot about how much heat your CPU generates. This video from LinusTechTips helps you understand how to pick the right heat sink, and more importantly, how to improve the one you have.
As the video points out, small imperfections in the surface of a heat sink, as well as the shape of the heat sink, can have an impact on the heat dispersion. In particular, convex-shaped heat sinks have a slight advantage, while concave heat sinks are at a disadvantage.
You can also use a process called lapping to refine a heat sink that has a lot of imperfections. Not everyone will notice a difference -- LinusTechTips tried it and found exactly zero change -- but that may just mean you have a good heat sink.
One that has flaws that disrupt the contact between the sink and the CPU can be improved with the process of lapping.