Passive Solar planning and design depends on a dimensional understanding of sun path, site and season. Start with a sun path diagram. Factor in a point of orientation on the site. Imagine the solar radiation on that point over time (through the changing seasons). It can be quite daunting because to be strictly accurate the model needs to be run for each significant point on the site or on the building(s) in question.
One of the single best general sources I have found on sustainable architecture in general is a publication from the Los Alamos National Laboratory. Appendix G of that publication graphically describes the modeling required to understand, visualize, orientation in passive passive solar design. The graphics in this publication are very well done, including beautifully drawn visualizations of the sun path diagram (which has been a staple of astronomy and projective geometry since the Renaissance). Two are reproduced here.
On a humorous note: The shading diagrams from most texts (and much of the internet) are misleading. These tend to use the wrong dates for calculating overhangs. Can you say why?
LANL (Los Alamos National Laboratory). Sustainable Design Guide. Los Alamos, NM: US DOE, 2002
www.lanl.gov