Planet in Illustrator Tutorial

 

 First, create a circle by using L and holding down shift while you drag to maintain a perfect circle.  

Then, create another circle, but remove the fill to make it an outline. Go to Effects > 3D

It'll initially look like this. 

Rotate the cube with your cursor to alter the three dimensional point of view, until it's tilted in the manner you want the rings to be.

Resize the stroke size of the outline until it's thick enough.

Select the knife tool, and divide the circle in half. Bring the top half to the front with Arrange>Bring to Front .

Adjust the ring until it appears as if it is around the planet.