The first resource is the PEP 8 style guide itself. It can be accessed at Python official website.
Datacamp also hosts a neat and simple PEP 8 tutorial on their website.
YouTube also features a bunch of PEP 8 tutorials. However, while trying to internalize all the PEP 8 guidelines, it is easy to get swayed by the technicality. The following presentation by Raymond Hettinger at PyCon 2015 helped me a lot to understand how to strike a balance between the need to write intelligible code and beautiful code.
But these are all tutorials. What about tools that would help in writing PEP 8 compliant code?
Some of the tools that come in handy for PEP 8 style checking include: