Blogging as a Professional Goal

As a newcomer to the math teacher blog community, I have too many big ideas to try this coming school year.  I say too many because I know myself too well to think that I'll follow through on all of the potentially valuable strategies I've collected from the blogging superstars.

So, like most any district, I have to determine a goal at the beginning of the year, implement and document the heck out of it, and show amazing results at the end.  You know, the one where regardless of whether it was a successful strategy, you have to scramble to put together some concrete "evidence" that it promoted student learning.  I'd say most of us very subjectively determine the successes and failures of our strategies - I always have great intentions of recording student input and personal reflections, but again with the follow-through... 

I really want to use my reflection blog as my professional growth plan.  In my mind, it's awesome because the teaching strategies can be fluid and varied and I'll be forced to document in my blog.  Beautiful.  Where I need help is:
How do I document student achievement as it relates to my blogging goal?

Hmmm...