Paying attention to the monsters that give you/point you to chests and such is really key. (Sorry if I’m explaining stuff you already know!)
Spoilers
Like Minotaurs (6) always have a chest in one of the three spaces behind them, the knights Romeo and Juliet (9) always give you a heart scroll, there is always an egg (0) in a space next to the dragon that gives you exp. The mine master (10) (or whatever they're called lol) is always in one of the corners and transforms all mines into exp.If you go through the comments, other people will also have more and better explanations and tips.