[Andy]

If you require more detail it's easier to add it to the side of your car/shape before you do the extrude. Do this by dividing surfaces or inserting extra vertices.

A good way to add extra detail later is to divide all surfaces. This gives you a new centre point in each surface.

Selecting your surfaces and vertices may be easier from the 3d window - hold down control and click/drag over the surfaces/vertices you want (note that a click will select only the nearest whereas a drag selects everything under the area).

Hope this helps,

Andy