Boot options
While starting press the following keys:
Option – lists all bootable drives
D – Apple Hardware Diagnostic will start
N – Boot from Network
C – Start from bootable media
X – Force Mac OSX startup
T – Boot in FireWire Mode
CMD + R – Use Recovery
CMD + Option + P + R – Reset NVRAM / parameter RAM
CMD + V – Start in Verbose Mode
Shift – Secure Boot (Foldercheck / disabled unneeded Plugins)