Here's a Python 'tutorial' I put together to help our team better understand the algorithm described in the FIRST vision processing doc @
http://wpilib.screenstepslive.com/s/3120/m/8731, and the similar team 341 posted vision code.
Maybe you will find it helpful if you aren't past this point yet.
https://github.com/LiftingSea/frc_vision_tutorial
It also leveraged some of the OpenCV tutorials to open multiple windows for the various stages of the processing, and provide some knobs for experimenting with tuning the algorithm in real time.
I started writing it in C++ using just the open source gcc compiler, and, as mentioned in another post here, decided to take advantage of the interactive and friendlier Python environment.
The 'tutorial' involves running the program and seeing how the tuning knobs affect the targeting results, as well as some suggested 'next steps' for students to take in the comments at the beginning of the file, to facilitate learning by example.