I've heard, but can't prove it (nor did any research on it), that if you've been smoking for 'quite a while' that your metabolism processes it faster. Caffeine also speeds that up. Getting it out of your blood is a problem, so try lots of water (or drinks without sugar) but water's the best, and piss out as much as you can.

Remember that your piss contains very little blood, so you're gonna have to piss bucket-fulls.