A literary technique that Riordan uses is symbolism. One of the main conflicts in "The Lightning Thief" is the fact that Zeus's masterbolt is missing. It isn't just the fact that someone stole Zeus's most powerful weapon that is a conflict. It is the fact of everyone accussing each other. Zeus blames Poseidon and Percy while Poseidon blames Hades and demands an apology. The lightning bolt missing, stands for most of the conflict is this book.
Dreams play a role in the story. Percy has horrible dreams almost every single night. We learn that this happens to most demigods. It is a way of delivering messages from the gods, friends, or enemies. At one point in the story, Percy has a dream that revealed who the real enemy was (but then there was the Lotus Casino, which caused him to forget it).
A literary technique that is used a lot by Riordan is tone. Just from reading the table of contents, you can tell that Percy is very sarcastic. For exple take the chapter titles, I Become Supreme Lord of the Bathroom, We Get Advice From a Poodle, and I Accidentally Vaporize My Pre-Algebra Teacher. Also, Percy tries to act nonchalant about everything. In the very beginning of the book, he says "Look, I didn't want to be a half-blood." (Riordan,1). When he finds out his Latin teacher is actually a centaur, he says, "Once I got over the fact that my Latin teacher was a horse, we had a nice tour, though I was careful not to walk behind him." (Riordan, 75).