If you really want to know, you have to go to the sources.
Unfortunately there aren't a lot of elite training manuals out there. Look at all that you can find, there will be major differences.
For a little older school model check out Peter Coe's book and Harry Wilson's book.
Read Brad Hudson's book and Canova's marathon training book too.
As far as threads on letsrun, Canova's thread and the Cabral-Hadd thread are excellent.
The british milers club also has some good training excerpts from guys like Moorcroft that will show you their periodization.
I think Cabral and hudson do the best job of describing periodization in simple terms.
Generally, in the old days most coaches used a linear periodization (ala Lydiard), while most modern coaches now use a nonlinear periodization.