I'm afraid that the two answers above are both mistaken. I want to explain Kant's deontology rather than the unfortunate hangers-on who came later and seemingly never understood Kant's view.
First, you are right, as Kant explains time-and-again; consequences can never be part of the decision that something is right or wrong. Why? Kant argues that responsibility for being moral is possible only if we know with absolute certainty was is right and what is wrong. Consequences never give us that certainty. So, consequences never have any part in any moral judgment.
Second, deontology focuses on the logic of a moral judgment. Here you go. Suppose we allowed lying, so that instead of telling people they ought not to lie, we tell them that lying is fine. So we all decide to follow the moral judgment that "Lying is right." Now, when you tell me something, I consider that you might be lying, so I cannot EVER trust what you say. Because of that conclusion, I realize that you cannot even lie to me! That is, the rule that allows lying makes lying impossible. That is the logic that supports the moral judgment that lying is never right.
Anyone who says that deontologists are concerned with fashion or with self-righteousness might consider a career in mathematics and stay out of ethics. The point of the deontological theory is the argument used to prove the right or wrong of some action. Unless one can produce a valid argument—like the one I used for lying—about fashion, we can consider his ramblings as pure bovine spoor (BS).
So you want an example. Suppose I am hiding Jews in the attic when along comes a Nazi officer looking for Jews. He comes to my door and asks whether I am hiding Jews. I am confronted with the following decision: “Does morality allow me to lie in this case?” I reflect on the argument I showed you above and I realize that morality does not allow me to lie in this or any other case. So, the choice to lie is wrong and the choice to not lie is right.
No doubt you and others are aghast at this conclusion, thinking “Oh what a terrible conclusion. Deontology must be a wrong theory if it allows that conclusion.” You have decided to reject the logical argument proving that lying is wrong to favor your personal feelings that lying is not always wrong. So let’s look at your theory of ethics.
You have decided that ethics must be based on personal feelings, assuming the conclusions above. So one day I tell you that I have decided to take my gun and murder a family of Jews living down the street, maybe they are black people or old white men. (I am speaking of today, not in the 1930s or 40s.) You see, my personal feelings command me to murder them. You have no argument to prevent me from doing what I set out to do because you think morality is all personal feelings. If I must do what is morally right, and if it is morally right for me to murder these people because that’s what my personal feelings are, then I should murder them.
Moreover, you might focus on the consequences of my refusing to lie. But suppose that one of the children in this family of Jews I am hiding would have grown up to become a mass murderer if he survives. Suppose that the Nazi officer is secretly opposed to the murder of Jews. Whenever someone tells him they are hiding Jews, he quietly walks away. Whenever someone tells him they are not hiding Jews, he barges in and inspects their house. So, my lie could cause him to inspect my house, find the Jews and then be forced by his superiors to have them carted off to the camps.
You see, morality cannot be based on personal feelings or on consequences, and that is why I am a deontologist.