Microsoft ASP.NET Coding Strategies with the Microsoft ASP.NET Team (Pro-Developer)

Performance tuning should not be postponed until you’re faced with a serious problem on a live site. Instead, you should consider the issues throughout site development, starting with application design. Performance tuning is an iterative process. The first iteration should be to ascertain the exact behavior of the application. You do this using load-generation tools in a controlled environment while monitoring performance counters and examining page-tracing information. Time-to-first-byte and time-to-last-byte measurements are indicators of application responsiveness and the duration of page execution.

After you assess the problems and make changes to the application, gather performance data again to accurately ascertain the effects of your modifications. Employ caching where possible to eliminate unnecessary code execution and database work. You can make additional gains by improving your coding techniques and eliminating unnecessary view state and session data.