When I was a kid it took me a long time to learn this. So, I thought it would useful to put a link to it here. The transformations are from rectangular to polar, cylindrical and back in a useful structured approach.
This is a link to Dan Fleisch’s site for his book. He is an Associate Professor in the Department of Physics at Wittenberg University, where he specializes in electromagnetics and space physics. He is the author of A Student’s Guide to Maxwell’s Equations published by Cambridge University Press in 2008