To give a concrete example; i had some experience in network programming/protocol implementations before i came across this book. In the "Notations" chapter, they show network message pack/unpack routines written in the style of printf/scanf functions with format strings specifying the packet layout! This was a eye-opening lesson for me in the use of proper notations and little languages. There is also some code snippet examples showing ideas behind Virtual Machines, Code Threading, JIT compilation etc.
Folks should also get Kernighan and Pike's older book "The Unix Programming Environment" to go with this. The chapter "Program Development" gives a complete example of developing a compiler for a small calculator language using compiler development tools (and no theory!) in around 50 pages. This is the smallest and simplest exposition that i know of on how to write a compiler.
In summary; get all of Kernighan's books and study them! :-)