[Alert: this article might be Startups-oriented and presume readers to have basic understanding on related areas. Still, no worry, it's totally okay if you're not one, simply skip directly to the "Solution" section and grab the insight as quick takeaway. Then just leave the rest as bed-time story later. ;) ]
Cohort analysis has been a very hot topics in Analytics & Startup era, especial after Eric Ries published his startup bible: Lean Startup. Need not to say, it's a powerful tool (otherwise why a hot topic?). For those who don't know anything about such methodology, originated from Medical field, a cohort means grouping certain subjects (usually people), based on certain common characteristics (says, user experience that we've delivered) within a defined period (ref: Cohort Study - Wikipedia: http://bit.ly/XZn5Fb); and a cohort analysis will be analysis performed across different cohorts. While it might be somehow confusing, simply speaking, cohort analysis allows us to understand behavior of groups of subjects, specified by time, over time.
Got it? No? Don't worry, since we've plenty of articles out there which talks about this topic (see the end of article), i might cover this area more later but not today. Today, we focus mainly on how to prepare proper installation for Cohort Analysis, using Google Analytics & client-side javascripts, in a quick and dirty way.