Hi!
In our SaaSy webapp we need to collect Google Analytics-like data (like, what pages were visited, how many 404s where there, etc.). I wonder if there are any best practices on what pieces of information should be collected (like, IP, User Agent, etc.) and how should these logs be stored. Requirements on what statistics we're going to display are not yet fixed, but I want to have a starting point.
Can you help me out with this? Thanks.
Tracking for the sake of tracking is pointless. The point of tracking activity on your site is to answer specific business questions, such as how many people are buying your product, or how far are they getting in your sale funnel or other events like signing up for a newsletter, etc...What you should be doing is asking the people who make business decisions what it is they need/want to know, and go from there.
Having said that, most ad-hoc reports can be generated with basics like the URL and timestamp. Ability to parse specific variables from the URL and categorize them and their values is handy for campaign tracking. Tracking IP addresses are good for debugging and finding out what country/region/market the user is coming from. Referring URL is good for tracking where the user came from on the internet (another site, paid vs. organic search, a campaign, etc...).
And then throw a couple of variables into the mix. Allow for the ability to populate variables with arbitrary information (like product IDs, etc...) that can be sent to you and stored, so you can see things like how many times a product was viewed or purchased, how much it cost, etc...
But anyways, to answer your question, ultimately "best practice" is first sitting down with the guys in suits and ask what they want/need to know and work with them to find out if what they want to know is just silly or if it's actually actionable (for example, knowing things like number of pageviews is okay but how actionable is it really? What's MORE actionable is knowing how many of xyz is being sold, or where on your site people are abandoning you, so you can streamline your site, maybe decide your product or offer sucks and needs to be revisited, etc...).
I have to ask though...is there a particular reason you wish to create your own tracking tool as opposed to using or investing in one of the many tools already out there? There is Google Analytics (GA), Yahoo Web Analytics (YWA), Omniture SiteCatalyst, Webtrends to name a few. Some are free, some cost money, but it is an investment that yields real returns if used properly.