A lot of the "how to" guides on the internet are useful, but some aren't particularly fun. Lying can be thrilling if your dumb ass doesn't screw it up. Here are some rules to live by when it comes to fibbing.
Dumb it down - Try not to use big words when lying. If your sentences are structured in a sophisticated manner and your vocabulary is not your ordinary one, people will realize that your thinking extra hard about the exact words that are coming out of your mouth and will catch on to your farce.
Avoid/Maintain Eye Contact - Avoiding eye contact will show that your lying as you're trying to gather your thoughts and can't bear to look at the person to whom your lying. Alternatively, maintaining a strong and steady eye contact can screw you over just the same. A gaze (especially a suspicious one) is a very intense stimulus and puts added pressure on you when you're lying. So how does one avoid both problems? Stare at your victim between the eyes or, better yet, focus your gaze just above their left eye. People tend to look up and to the left when they're recalling a memory and up and to the right when they're construction one. This has to do with the hemispheres of the brain but I don't want to get into that.
Shut Up and Speak Up - Being too quiet and being too talkative are both signs of a liar. A quiet composure will make you seem like your trying to end the conversation as you realize that your stuck in a lie and can't make anything up. On the other hand, talking too much makes you seem like you're overcompensating and are trying to talk your way out of the lie (similar to buying your way out of a bluff in poker). To stay in the safe zone, be firm about your facts but don't over indulge.
For example this is a bad lie:
"Where did you go this weekend?"
"I hit up club Vatican"
"No you didn't. I was there and didn't see you."
"I left early because I was feeling sick from all the alcohol. I decided to call a cab before the party started"
This is a better one:
"Where did you go this weekend?"
"I hit up club Vatican"
"No you didn't. I was there and didn't see you."
"I left early because I was feeling sick"
"From what?"
"Too much alcohol"
"Who drove you then?"
"I called a cab before the party started and the streets got crowded up."
Even if you have a whole story made up, hold onto it. Letting the information go as it's asked gives the impression that the answers are impromptu and honest.
Hands off - The trickiest thing to control in a lie is your hands. Once you're conscious about your hand placement, you won't know where to put them. Crossing your arms creates a makeshift barrier and is a telltale sign of a liar. Touching the face is another big no-no. Instead, you could put them on your waist or relaxed to your sides. Always have them in full view. For those that know what to look for in a liar, the hand gestures can be an easy giveaway.
Pay Attention to Detail - Giving minute, insignificant details is a good way of convincing a person. If you show that you can retell such an anecdotal part of the story, then surely it must be real. Never leave the details open ended because you never know when a follow up question could be thrown your way and throw you off guard.
Watch for Traps - In cases when your victim thinks they have caught you in a lie, they will ask you to re-state a point you made earlier so that they may catch you in a clear cut lie. Be extremely careful, this could bust your whole act. Before repeating a statement already made, think about what they are asking and if they might be able to call you on it.
Trapped Example:
"You say you left the club at 8:30?"
"Ya"
"That's impossible, I was standing outside the club at 8:30"
Near Miss Example:
"You say you left the club at 8:30?"
"I think I did, I was too drunk to accurately guess the time"
"Ah, I see."
A person that has fully bought on to what you are saying will never re-ask a point that they have clearly understood. Don't mistake this for a nice recovery. You still screwed up and now you're just lessening the damage it causes. You're going to need to sound pretty convincing to win back their trust.
Hopefully, if you keep these ideas in mind, you should be able to survive this world full of weasels (of which you are now a part). Enjoy.