when i explain how to flash to someone else I pull out all the safety warnings. I'd rather be safe than sorry when dealing with someone else's equipment. I'm a little more sloppy on my own system.
i always tell people to flash in safe mode and remove all discs even though I never flash in safe mode. (I do remove discs however)
I also tell them not to touch the computer until they get the message that the drive has flashed successfully even though I've been known to multitask.
basically, if the power gets cut while you're flashing then your drive will be a fun experiment to try to get working again. I don't know how people do it, but buttons are accidentally pressed or they "forget" they're in the middle of something and reboot while flashing and BAM they come whining that their drive is broken.
basically if you have a stable system and your house doesn't look like it's about to be struck my lightning any time soon go ahead and flash in normal mode. It cant hurt to remove the discs from the drives, but don't freak out if you forget to. do whatever you want while flashing, but always wait until you get the successful confirmation before rebooting.