Are you working in the week? You could play it all week saying you feel like you're coming down with something, then the day before the day you want off you could get sent home
I was watching Sky News before and apparently there are some good tips on the Benilyn website. (Some cold medication-probably spelt that wrong by the way.)
Don't do it! I was a silly monkey. I called in "sick" and them went to the cinema with mates. While we were in tesco shopping for sweeties and stuff, we bumped into my boss...