How to convince your co-workers that you are a dirty stop-out in six easy steps.

1. Wear the same clothes as you did the day before. This may sound obvious. But to really pull off this look you have to be wearing trousers that get baggier as you wear them, so after a day they are falling down just a bit. After two days? They must be so loose that everytime you stand up or, heaven forbid, try and walk anywhere, you have to loop your thumbs through the top as if you might unexpectedly break into a Dick Van Dyke-style kicky dance.
2. Have lip balm smeared over your face in lieu of moisturiser, because it is either that or watching as your face cracks off and shatters into little pieces on the floor. This will achieve a pleasant 'oily', or 'greasy' look. Either Vaseline or the stuff they gave you to put on your tattoo, called Tattoo Goo, will do this nicely.
3. Sit at your desk motionless for at least half an hour, preferably staring/squinting at some point in the middle distance, even though you bought the office milk on your way in to work so nobody can have tea or cereal until you stand the fuck up and kicky-dance your way to the kitchen.
4. Get caught trying surreptitiously to put make up on at your desk, cowering behind your computer getting foundation all over the place because your motor-skills have been seriously compromised by alcohol and lack of sleep.
5. Have terrible hair. Constantly remind yourself that, actually, your hair always looks this terrible and your co-workers would think it much more odd if you had good hair one day. Feel a bit glum about this for a while until you forget what you were feeling glum about. Resume staring/squinting.
6. Crawl under you desk and curl up as small as you can. Shut your eyes very, very tight. Hope fiercely that if you can't see your co-workers, they can't see you.

Easy, see?
This, of course, is all pure speculation, and certainly NOT from first hand experience.
I am chirpy, immaculately dressed, and have sleek, groomed hair. I had ten hours solid sleep, rose at six, did some yoga, went for a short invigorating jog then had some muesli, followed by a refreshing shower and a meeting with my stylist.