Until we're all totally rich and can afford custom suits or have perfected our own tailoring skills, most of us will have to make do with off-the-rack traditional men's clothing: suits, dress shirts, pants, etc. And since there's like a trillion little pins and plastic things all over every item in the department store, it helps to know your basic measurements before you begin to try things on.
Every man should know a the following measurements: chest, sleeve, neck, shirt size, waist, inseam, and shoe sizes. And, in order to get these things to fit properly, you need to measure yourself properly.
The Art of Manliness has come up with the ultimate guide, and have even included a little card that you can fill out and keep in your wallet for whenever you need it.