SECRET #1: Have a reason to lie (and lie no more than needed)
The bad liars tell lies even when they do not have to, then have to cover up lies with even more lies. Eventually they told so many lies, cannot keep their story straight, and their lies are exposed.
The good liars lie just enough to achieve what they need.
SECRET #2: Lay the groundwork
Liars who have worked out their story beforehand, instead of extemporizing (i.e. making it up as they go) enjoy far more success with their lies. As always, practice makes perfect. It also helps them be consistent (see Secret #5)
SECRET #3 Tell the truth, but presented in a misleading way
Technically, half-lies are not outright lies. They did tell you the truth, but in a way you thought the statement meant something else.
SECRET #4: Know your target, and tailor your lies
Good liars can get inside listener's head, not literally of course. By using empathy, a liar can pick up what the listeners want to hear, and avoid hitting trip wires that will trigger their suspicions.
SECRET #5: Keep your facts straight
Successful lying is hard because you have to be consistent. If you say one thing at one time, and another thing at another, then people will catch you in a lie.
SECRET #6: Stay Focused
How committed is the liar to the lie? Most people find lying unpleasant, and when they finish lying they felt relief. Good liars, on the other hand, enjoy lying, and feels no shame or remorse.
SECRET #7: Beware of non-verbal signals
The bad liars fidget when they lie. The really good liars can control their non-verbal cues, thus NOT giving away their lies.
SECRET #8 Turn up the pressure
Raise the emotional stakes when the target becomes suspicious, to distract the target.
SECRET #9: Counter-attack
Most people are uncomfortable accusing others, and this can be used by a liar to their advantage. By attacking the critics, the liar can force the critics back on the defensive, by introducing doubt. Was the critic really justified in doubting the liar? Uh...
SECRET #10: Bargain
Good liars can often "bargain" their way out of a jam, even when they were caught in a lie, by eliminate feelings of responsibility for the lie. This is often done by passing it onto someone else, or pay off those who were offended.
ref: For "10 secrets of an effective liar", see Psychology Today / Extreme Fear Blog / Top 10 Secrets of Effective Liars.