This tutorial is probably already on this forum, but i just found out how to make these things using curves only, this makes it take up much less memory, and is quicker and easier to make.
1)Delete the default cube
2)Press spacebar+Add+Curve+Bezier Circle
3)Add another one and scale it down using S
4)Duplicate it, using Shift+D, and move it near the edge of the first circle, and scale it down
5)Duplicate it 3 more times, to make it look like this:
6)Select all of these small circles, using Shift+Right Click, press . (the period key), and duplicate it, press R, Hold Ctrl, and rotate it in 30 degree intervals around the whole circle.
View the next post to see what to do next.