Summarize:

After you tell the lie, you may be asked to tell the story again, or give a fuller explanation. Do not back down and take back the lie you told. Stick to it and repeat it as closely as possible to the way you told it the first time. Asking the same question multiple times is a tactic to get you to give up the lie. When you are asked for more information, don't add too much to the lie so that it becomes complicated. Do your best to add one small piece of information that will enhance the lie but not make it too hard to maintain. Sometimes you can disorient people and distract them by answering a question with another question. Say something like, "Why don't you believe me?" or "Did you hear a different story from someone else?". This puts the person questioning you in the hot seat to answer. This will make the other person think that your lie was just their imagination. Beware though- as this doesn't usually work that well, and if it doesn't, you can get caught.
Stick to your story. Add a small extra detail. Answer the question with a question. Say you don't remember telling the lie if you happen to almost get caught.