Method 1: Hold CTRL
When you hold the CTRL button on your keyboard when clicking the Outlook shortcut on your Desktop, Taskbar, Start Menu or Start Screen, Outlook will detect this and asks if you want to start Outlook in Safe Mode.
This method works in all versions of Windows and for all versions of Outlook.
Method 2: Windows Vista and Windows 7
If you are using Windows Vista or Windows 7, then there is a Search box in the Start Menu. Here type; outlook.exe /safe
Method 3: Windows 8
In Windows 8, the search box will automatically show when you start typing. So simply open the Start Screen and type; outlook.exe /safe