How can I start Ubuntu in Safe Mode?

To start Ubuntu into safe mode (Recovery Mode) hold down the left Shift key as the computer starts to boot. If holding the Shift key doesn't display the menu press the Esc key repeatedly to display the GRUB 2 menu. From there you can choose the recovery option.

On 12.10 the Tab key works for me.

I got it to work by pushing the SHIFT & ESC keys, but it didn't seem to work until the second boot load screen that comes after the screen where you have the option to press f12, DEL etc.

os : elementary os hera (ubuntu derivative)

-method 1
first boot:
press the escape key to enter the startup menu then enter normally the os login manager , then restart
second boot:
press the shift key , it will redirect you to the gnu grub screen

-method 2
turn the power on then press&hold the shift key , then one simple keystroke at the ESC key