The 50-50-90 rule: Anytime you have a 50-50 chance of getting something right, there's a 90% probability you'll get it wrong
Don't tell a lot about yourself, behind your back will tell more interestingly about you
I rang up British Telecom, I said, "I want to report a nuisance caller", he said "Not you again"
Patient: "Doctor, I get heartburn every time I eat birthday cake." Doctor: "Next time, take off the candles."