Quote Originally Posted by Spuddles View Post
Don't use spells that have saves on dragons. It's not worth the spell slots and actions.

Unless you can guarantee very high DCs.
Nitpick: Don't use spells which are completely negated by a save on dragons. If you can tricks to get off two spells like Ray of Exhaustion, then wham, you got an exhausted dragon, save or no save. Or you have an exhausted dragon and an extra action, if you get lucky and it fails its first save. Don't, however, use spells which are completely negated by saves, like charm monster.