when battling the Ender Dragon always make sure to bring a bow and arrow as it can come in handy when destroying the Ender crystal on top of Obsidian towers. It can be tricky to get rid of caged ones but if you are a good archer you can shoot an arrow inbetween the bars to hit the Ender Crystals. Also, never attack the Ender Dragon when not all the Ender Crystals have been destroyed. The Ender Crystals heal the Ender Dragon and also explode upon being destroyed.
There are many Endermen roaming around the end so make sure to bring a pumkin (this can block some of the screen so you can only see through the eyes and mouth of the pumpkin but will protect from endermen) because if stared at directly through players eyes they run and attack you and if you are on only a couple of hearts this will make you possibly lose all of the items you had brought.
Finally,Sometimes the the Ender Dragon will drop down from the sky and rest on the portal that gets you home and goes through the credits as you hop into it after beating the Ender Dragon. This is a crucial time to miss as you can shoot many arrows at this moment. But as soon as he lands, he is invincible to projectile damage. He only does this for a short amount of time so make sure to take this moment and try and kill it.