There's lots of tutorials on how to make a realistic earth in other 3D programs but I haven't seen one for Cinema 4D. The principles for all these tutorials are the same so I've adapted these tutorials into one for Cinema 4D
Although this may seem like quite a specific tutorial the techniques you will learn translate very well for other things, you'll learn about some of the special shaders Cinema has and how to create multi layered materials.
Please comment if you think I can improve anything with my videos or if you have any questions!
and if you need the textures for this, they are over on my website, andrew-wade.co.uk