One of the people on the Nintendo Papercraft forums asked how to create a sphere in SketchUp.
Everybody has their own preference on how to do this, but I like to use the "Follow-me" tool. ;o)
You can also simply import an existing one as a component by going to the "Window" menu, opening the "Component" window and then chosing "Shapes" from the pulldown menu, but if you want a bit more control ( I like to unfold spheres as "rings" or "petals" for instance ) you can also easily create one yourself.
I wanted to show inexperienced users why the "Follow-me" tool is called the "Follow-me" tool, but you can also simply select the circle, and then click on the perpencidular semi-circle with the "Follow-me" tool, and then the semi-circle shape will automatically follow the circular outline all the way around to create a sphere.
Especially on very complex shapes, that's much easier of course (although sometimes you'll still want to do it manually ;o)
I always think the best way to learn a software like this, is just to play around with it whenever you have the time; it's a lot more fun that way and you'll often find your own way of doing things, that works much better for you than the one explained to you by someone else! ;o)
But if you still need some help, SketchUp has *a lot* of video tutorials that can offer some much needed explanation of course: [link]