I often start with a 3-view picture of some object (such as the airplanes), and use Corel to convert the drawing from a bitmap to vector form. Then I load the vector image into TrueSpace, and start extruding the various pieces.

A few good sources for drawings are:

Once extruded, I use the intersection operator to weld the 3 separate views into a single 3d object. That part is pretty easy.. it's after that when you have to spend serious time refining the curves to make them look proper.

If the methods above aren't clear.. walk thru the Tutorial.  I'll be adding more material as time goes along.

The real problem then begins.. dealing with the Design Limits.