Disclaimer: I don’t recommend lying. It’s wrong and it’s risky. You’ll feel bad about it, depending on how much of a conscience you have, and the more you do it, the greater the chance someone’s going to catch you. That being said, if you’re going to lie… do it well.
If you can think of it, someone else will.
If you’re going to lie about something (and have the opportunity to think about it beforehand), consider every possibility.
Every single possibility.
If there is a small detail that someone can see as inconsistent, figure out a way how it fits into your overall story you’re creating. Think of it as being the director of a movie; your job right now is to eliminate every single plot hole. Every unvisited corner of your tale needs to be tightly locked up.
You need to do this. If you think “nobody’s going to pay that much attention to my lie” you are wrong. The worst part is that you’ll never realize how wrong you are for a very long time. People are suspicious of you in their own minds long before they say anything. And they’ll gossip about you behind your back long before anyone tells you to your face.
You need to consider every angle where your story can be seen as less than perfect. It has to be literally perfect to be truly successful. It’s worth the extra thought.
For example, you’re pretending to be sick. Don’t go out shopping or anything. Yeah, it seems obvious, but people do this kind of stuff all the time. They put themselves in opportunities to get caught.
If you’re pretending your school paper is actually done, think of what you wrote it about. Yeah, of course you didn’t actually write it. But think about the details of the paper you’re imagining you wrote. (This goes back to believing that your own lie is actual truth.)
I am so against cheating in every aspect of the concept — just break up, already. But if you’re going to do it, think about every single detail that can go wrong. This is a good example for this post, because there’s so many little things in play:
Can she smell the perfume on you? Can she smell smoke from the bar? Where were you? If you’re going to say you were with friends X, Y, and/or Z, but you actually weren’t, that is a plot hole. And that is dangerous.
Do you keep condoms in the house? Did you take some with you? If she goes into that drawer, will she notice that the condoms were disturbed or moved slightly? Or that there’s less of them?
Eventually, all those late nights spent “at work” will be less believable when you don’t actually get the promotion you should have gotten from working all those extra hours.
Check out my original, slightly more esoteric “Don’t leave room for failure” advice post.)