1. Don't hover in one place. Always be moving. Ballistae shoot in a straight line, and the spear travels slowly, so dodge it.
2. Immediately after the dragon battle starts, open up your inventory, use any dragon skill books you have, and put on your armor (you should have a complete Dragonbone set by then). Assign all dragon skill points you have to Fire Sphere.
3. Dragon Armor will give you more HP and some bonus skills. Map your new skills to your quick bar right away.
4. Also, put a healing potion on your quickbar. Yes, you can use healing potions still. You don't need mana potions because the dragon regenerates mana super-quickly.
5. Fire Sphere is an iWin button. It's a homing missile. As soon as you lock on to something, shoot it and dodge. Any return fire will miss, and your fire sphere will chase the target and hit.
6. Kill the nests right away. As soon as you lock on to the nest tower (blue circle), fire the Fire Sphere, then dodge, and come around for another pass.
7. Your fire breath is a default attack, you fire it with left mouse button. It burns down towers pretty quick if you get close and then circle-strafe around the tower. But you have to be pretty much point-blank. Ballistae have some trouble shooting point-blank.
8. If the lock-on circle is blue, it means that you can hit it with Fire Sphere. If it is red, you can hit it with Fire Breath and Dragon Burst.
9. Dragon Spirit is your heal. It has a long and asinine cooldown. Use it if you have no potions or want to save potions for later.
10. Dragon Shield is not AWESOME, but it will help if you are taking it from all sides.
Above all, DO NOT HOVER. You are a speedy beast, so don't stay in one place, strafe a lot, watch for the ballistae spears and dodge them.