The proper way to handle an alignment change is to give the player the option of opening the character sheet, clicking on the character's alignment, and selecting "new alignment" from a menu. The point of an alignment is that it's a statement from the player about how he or she plans to play the character. This is an opportunity to tailor the game around the players experience. Instead, it gets treated as a scorecard in a pointless minigame, or worse, as an excuse for lots of irrelevant nonsense.
For example: a beggar stops you in the street and asks for a coin. You have the choice of (a) giving the beggar a coin [good], (b) saying "no," [neutral] or © kicking the beggar in the face [evil]. Your choice does not matter in the slightest, so why is it even there? to let you "roleplay?"
The answer is that it's there to let you feel like you have a choice without giving you one. You're not fooled, of course, because it's a meaningless interaction, and you'll never see the beggar again. But your character has theoretically become "more good" or "more evil" and you're supposed to be satisfied with that.
Suppose, instead, that a game (a) never changes your alignment for you, (b) gives you options based on your stated alignment, and © makes sure your interactions are meaningful.
Well, we can get rid of the beggar encounter. There's only one response per possible alignment and it was irrelevant anyway, except to make good people poorer. Instead, let's look at the character's alignment. Hm. Chaotic evil.
Well, that says he prizes himself rather more highly than he prizes other people, and he's not one to get stuffy about laws being broken. Let's say he's walking past an alley and he overhears some thieves busy discussing a planned job.
He could (a) keep walking, (b) offer to join the thieves for a small cut of the loot, © offer to lead the thieves for a big cut of the loot, or (d) rob the thieves -- what are they going to do, call the guards?
For Mr. Lawful Good Paladin, on the other hand, nothing happens. He can walk back and forth in front of the alley all day -- it's empty for him. He really has only one choice -- demand the thieves surrender, then kill them when they don't -- and so it's not meaningful. Instead, he gets to defend the innocent man being marched off to the gallows, over by the city hall.