Some notes for stuff I’ve experimented with but haven’t made “official” yet.
Initial split and shape
In top view, extrude two equal size boxes above and below initial box (select side vertices with "limit selection to visible" off, E, hold Ctrl, drag). End up with five boxes in a row, oriented vertically.
Drag vertices around to roughly fit shape of car, switching views as necessary. Actually this might be a good point to explain window splitting, set up and save a four-panel view. Show how to switch between configured views (once I figure out how to do it).
Adjust view to see front, back, and rear of car. K for loop/cut menu, knife midpoints (also experiment with loop cut, which cuts the entire model nicely), then place line segments to split all the way around the side, enter to create new edges. Drag to fit model. Do the same along the top (be careful with the bottom faces).
Wheel Wells
Make sure “limit selection to visible” is enabled for this bit. Select a column of vertices that fall in the wheel well area, and merge them (Alt+MKEY). From the bottom view (how to easy get to this view?), switch to edge mode, select and knife cut the internal edges, and then drag the vertices to the back of the well. Refine as needed.
I think I should do the wheel wells by tessellating the side panel, putting the vertices along the edge of the well, and then deleting the polys inside the well. Then select all of the edges and extrude them back into the body. I think.