I've had so many problems with this (usually with page load events being executed before button click events from the previous page) that I decided to look it up and post the event loop ordering:
Method Called Controls
------------------------------------------------------
1. Constructor Always All
2. AddParsedSubObject Always All
3. DeterminePostBackMode Always Page
4. OnInit Always All
5. LoadPageStateFromPersistenceMedium Postback Page
6. LoadViewState Postback All
7. ProcessPostData1 Postback Page
8. OnLoad Always All //Page Load
9. ProcessPostData2 Postback Page
10. RaiseChangedEvents Postback Page
11. RaisePostBackEvent Postback Page //Button Clicks
12. OnPreRender Always All //Put page load events here
13. SaveViewState Always All
14. SavePageStateToPersistenceMedium Always Page
15. Render Always All
16. OnUnload Always All