From Start Menu Settings, you can assign a hotkey of your choice for the Start screen. Look for the setting called "Additional Start screen hotkey". Or you can simply create a shortcut as follows:
Code:
"C:\Program Files\Classic Shell\ClassicStartMenu.exe" -togglenew
and pin it to the taskbar to directly open the Start screen if Shift is not suitable.
If you download the latest beta:
http://www.classicshell.net/downloads/latestbeta, you can just right click the Start screen shortcut inside the menu and do 'Pin to Taskbar'.