This must be done after pulling the battery! If you do not pull the battery, you will boot up normally.
-Hold down Volume Down Button + Power Button long enough to boot to HBOOT.
-If you booted up normally right away, you did not pull the battery or are probably connected via USB.Use the volume buttons to scroll and the power selects your option.
If selected stock recovery:
-Wait for stock recovery to boot (wait for red triangle with explanation point), once loaded, volume up button + power button will bring up stock recovery menu
-Use volume buttons to scroll, power button to select option.
OR, if you wish to accomplish this the nerdy way and you have already set up the Android SDK, you can use these adb and fasboot commands:
For Recovery (even with custom recovery flashed):
adb reboot recovery
To simply reboot from bootloader/fastboot modes:
adb reboot bootloader
To simply reboot from powered on state: