The lights are on
[Original poster] Mostly when you fight Ganondorf in the final battle just keep on using your shield, roll in between his legs then slash at his tail.
[Edit] Evasiveness is definitely key here. Ganon is a beast, and he will make Ali look like a featherweight, so keep your guard up! You'll want to enter the battle with as many fairies as you can and don't be afraid to use your shield spell.
However, if you're the type of person who prefers offense to defense, don't be afraid to shoot a light arrow at his face. This will sometimes stun him, allowing you to shoot his tail (it will be visible if you look between his legs, meaning you don't have to move once he's stunned).
After getting the Master Sword, rush headlong at him, roll between his legs and finish the job.