Reddit mentions of Design Drawing

design drawing

(not an architect, but it was helpful to me. may be more general than what you are looking for, but does include sketching.)

Design Drawing by Francis Ching
http://www.amazon.com/Design-Drawing-Francis-D-Ching/dp/0470533692

He covers perspectives and a host of other architectural drawing types, as well as things like line weight, tone and shading.

Also Architectural Graphics also by Ching.
http://www.amazon.com/Architectural-Graphics-Francis-D-Ching/dp/0470399112/ref=pd_bxgy_b_text_z

Architectural Graphics

Freehand Drawing for Architects and Interior Designers

Design Drawing

These should provide plenty of foundational skills and examples of the kinds of handdrawings you may find useful.

I'm taking the pre-architecture courses now, and I've recently graduated from a computer drafting program (AutoCAD and Revit with some Sketchup).

If I was going to start over again, I'd want to know how to draw. Definitely develop good line control (through contour, blind contour, and just line drawing exercises).

Model building is another important aspect. It's all about craft and getting familiar with the materials. You may end up using other materials but foamcore and basswood are the two go to materials in my classes.

For now, and my knowledge is limited, if you're going to learn any software, I'd focus more on Photoshop, Sketchup, and Rhino.

Helpful books would be Form, Space, and Order, Design Drawing and Drawing, A Creative Process all by Francis Ching.

I'd also study art and architectural history. Having a good knowledge base of different styles would help you in your own designs.