There are a lot of different things you can use to monitor a production ASP.NET web site for problems. Some of the most common are logging, perfmon counters and the like. There is also the method of getting feedback from people using the site when they relay that there is a problem.
The question I would like to talk about is how do you use this information for future projects.
Best Practices I think the most obvious way is the create a type of best practices document from the learning that you have had in the past. For example, using StringBuilder if you are going to be dynamically building up strings.
Code Re-use Another useful method is sharing code that is already in production so that other future projects can use it. This not only has the added benefit of less development time, you know this code has been running in production and will work correctly and not cause issues.
Analysis Sometimes yo ...
Go to the complete details ...