CDQs for alignment shifts aren't like CDQs for, say, a PrC, in great part due to the fact that Alatriel pointed out: alignment shift as a goal is OOC vs the much clearer IC goal of becoming a master of a blade or advancing one's ability to change shape.
A CDQ for an alignment shift will in fact have an IC goal that in itself has nothing to do with an alignment shift (I'll talk about that in a second). Rather, the situation leading up to the goal will offer opportunities to choose darker or lighter methods of accomplishing that end result. The point in an alignment shift CDQ is for the character to have to make that choice when multiple options are given to reach the same desired end. And ultimately, the character may in fact fail at accomplishing the goal, but shift alignment due to actions, or vice-verse, succeed in accomplishing the desired outcome, but see no shift in alignment, all due to the actions one chooses to reach the end.
The reason a CDQ for alignment shift will have a goal that isn't directly linked to an alignment (I.E. the goal won't be 'evil' if the aim is a shift toward evil) is because if you were already acting upon and recognized for performing goals under the blanket of that alignment, you'd already be that alignment. For example, the goal of a CDQ where the player hopes to shift his character toward evil won't be to murder a man in cold blood and return his tongue on a spoon to the Black Wizards. That's a goal for an evil character's CDQ. The goal of a CDQ where a player plans to shift his character toward evil could be to win the favor of a local lord by winning a cleverly devised and dangerous race. How the character chose to win that race, honorably or perhaps by cheating, would determine any manner of alignment shift.
This is why it may take more than one CDQ. Your character may be willing to cheat to win, but not quite yet willing to injure/murder his competitors. But after cheating and winning, maybe the character realizes, "Hey, that was much easier because I cheated, and no one found out." So in the next CDQ, he cheats again, only this time there's a chance to get caught. He can't risk that, too much is at stake, so he silences permanently the one who knows- an innocent man, no less. The character realizes he would do this again if it was required to save his own hide. Suddenly, the character has gone full-blown evil.
I hope that helps illustrate the sort of progression one may see during alignment shift CDQs. The key word here being, "progression."