How to create a 3D logo in Adobe Illustrator?

Adobe Illustrator isn't a 3D rendering program, so to create anything 3D in Illustrator requires that you simply draw it to look 3D.

How to draw something in 3D really isn't a topic specific to any particular drawing software, you just have to understanding some fundamentals of drawing...things like shading, color, shadows, gradients, highlights, etc.