I too like Jensen, but also try "Basic Blueprint Reading and Sketching" by Olivo. This is out of print - but search for a used copy. Used older books are fairly inexpensive, search for names like "Technical Drawing", "Engineering Drawing" or "Engineering Graphics". Sketching is an important skill but more importantly you want to make certain you can read the drawing and detail a drawing - whether you use a manual method or a CAD tool. I used to give my students a drawing and tell them to make the part in SolidWorks. If you want to see what our first level certification exam, check out the sample exam at
www.solidworks.com/cswa - you need to read a drawing inorder to make the model. Everyone who asked for sponsorship this year got coupon codes to take the CSWA exam for free. These are the skills our customers are looking for from young designers. It is not so important that you can sketch perfectly with a pencil - it is more important that you can interpret the drawing and create an accurate drawing with all the necessary dimensions and annotations. Marie