I started tracking my time for each NA in order to use the "balance" feature of Life Balance software, a pie chart showing time spent in each category, analogous to budget pie charts for personal finances. I do not log every minute of the day; rather, I note the time it takes to complete each NA on my lists. The first, most important benefit was that I gained a clear idea of how much time it takes me to complete actions and projects. The second benefit was that I learned how much time I "should" spend in certain focus areas each week in order to keep my longer-term goals on track.
I do not try to identify "time wasters." I don't really care how much time I spend surfing the web, watching TV, or chatting with friends, as long as I do accomplish the important actions and projects I have identified for the day or week.