The best way to learn is whatever is best for you. Depends too on the time you have and whatever other experience you have. C4D is not a trivial program, it has a lot of power and like all powerful/flexible programs it has a learning curve and often things can be done more than one way. It’s easier than some to learn but that doesn’t mean it’s easy.
Tutorials and practice, read the manual – hover the mouse over the parameters of any tool and hit F1 (cmd-F1 on Mac) and it brings up the help for that tool without having to search, that’s huge. Lurk and ask questions on the boards, there are books, free tutorials and paid tutorials and schools, some online (I think) and certainly some schools in certain cities.