I would suggest a large warning to always charge the battery completely before any flash attempt.
The phone cannot charge in bootloader and if you get stuck or need to reflash several times you can run the risk of a dead battery if the phone will not boot normally to recharge it.
Another important note is it is a very common misconception that flashing and SBF file completely restores the phone to a stock factory state. This is not true. Most SBF files and in particular official release builds do not write to cache or user data partitions by default and you must factory reset/wipe either in recovery or from the phone menu after flashing if you want a truly clean configuration.
Digital alchemy for the Droid and beyond.