1. Don't dress properly. If you want to get sick then make sure you're always wearing too little clothes when it's cold, and too many clothes when it's hot.
2. Work all day, don't take breaks. This includes lunchbreaks.
3. Don't eat anything. Who has time for eating?
4. Make sure you surround yourself with the most foreign bacterias as possible. Me? I did it by working at a kindergarten and surrounding myself with kids and then walking a dog in my lunchbreak.
5. Be outside all day, and run from place to place as fast as you can. Feel the wind blowing in your hair and the sickness taking hold.
6. If you have the possibility to travel to other countries to catch some foreign bacterias while following the steps above, I can almost guarantee your sickness.
7. Be sure to surround yourself with people who make you sick. People who you despise. And even if those people can't be there right then and there, try to picture them before you.
Good luck! I hope the sickness becomes all that you expected it to be:)