Is there a way to get Windows 8 to use my secondary monitor for the start screen?
The Windows Start screen's monitor placement can easily be toggled between multiple monitors.
When viewing the Start screen, press Win+PageUp or Win+PageDown to move it to the next monitor.
It will continue to open on the other monitor until you switch it back. Windows 8 apps (previously known as Metro Apps) will also follow the start screen and open on the second monitor.
Typically, Windows puts the start screen on whatever monitor is set as main.
To change which monitor is set as main:
I am not aware of any method that allows you to change which monitor the login screen is on without changing the monitor the start menu is on. Perhaps, one can write a script triggered by login. Perhaps another wonderful superuser can chime in below.