In 300, Leonidas tells the traitor Ephialtes to live a long life. At first it seems that Leonidas is telling him "Good luck with your life," a moment later Ephialtes breaks down in tears. Why? He was trying to regain his father's spartan honor, and in Sparta, you where only respected if you fought and died in battle. - Strilight
In the beginning Leonidas lures a wolf into a tight passage and spears it, because the wolf was basically trapped and helpless - he uses the same tactic during the battle of Termopilae: he lures the huge Persian army into a small space where they can't make full use of their vast numbers, and can only send smaller forces which get massacred.
How, exactly, does a society where the entire male population does nothing but train for war not just fall over? Of course, what the film doesn't tell you is that the only reason this was both possible and necessary was that the Spartans were horrendously enthusiastic enslavers, and treated helots with little more respect than animals: part of the agoge, the Crypteia, involved the students randomly killing any helots they met. Even contemporary Greeks were appalled by the Spartans' wholesale enslavement of Messenia, but mostly because they were fellow Greeks.
Quite possibly accidental Fridge Brilliance: Gerard Butler's frequent accent slippage actually puts his characterization of Leonidas in line with a long-standing Translation Convention. Spartans were often characterized as having Scottish accents when Ancient Greek plays were translated into English, drawing a parallel between how the English and the Scots regarded each other and how the Athenians and the Spartans regarded each other: prissy intellectuals versus short-tempered bumpkins.
Another case of Fridge Brilliance: The movie and the comic aren't regarded as very accurate in terms of historical events but rather a take on actual events put into a medium that makes for a fantastic story. At the end of the film the events are being told to Greek troops to hype them up for the approaching battle. The entire premise of the movie and the comic it was based on amounts to wartime propaganda to raise the moral of the home team!
Yet more Fridge Brilliance: Although the fighting was heavily stylized to the point of absurdity, when reading Greek literature such as The Iliad, one notices that the plot essentially stops for pages upon pages of gory descriptive combat. While the film may not be an accurate representation of Greek history, it does an amazingly good job of emulating the tone of Greek Epics.
The idea of Dilios making up details for the sake of rousing up the troops may have been true. During Leonidas' training, Dilios said that he was taught to show no pain... right as he is showing a pained expression as he is getting beaten.