I consider myself some sort of an expert at lying. Successful lying is actually textbook stuff:
1. Have a straight face and speak clearly
2. Say it confidently - with the true parts of the story with greater emphasis and lower your voice for the false parts
3. Reference to the above - no story can be completely false, do have some "universally true" statements within the story to make it believable - it needs to believably ambiguous
4. Most importantly, you have to believe in the story (for the time being) yourself!
Lying is very addictive. Seeing somebody believe a story you created has a very special thrill; making up something as you go along is much more fun (and riskier). Once I had discovered that I was good at it, I started lying about very mundane things, like,"what did you have for breakfast","which cricket team do you like" etc, just to see what limits I could stretch. The only thing I can say in my defense is that I never used it with an intent of malice.
Then there are those who are really good at catching lies. I have a lot of admiration for such people. I knew a girl in college who caught me the first time I tried to spin something by her (I was trying to describe my hometown), and I have respected her ever since.
I don't have a point to make here but I guess what I started out to write was that sometimes I feel incredibly guilty about lying and think about abandoning it altogether, and I am able to (atleast for a while); but life seems so trite and boring and mundane and uneventful, that I come back to it.
Therefore, lie but with care!