Obama joked with an unusually formal-dressed Zuckerberg that he is the only person who can get Zuckerberg to wear a suit and tie.

FORBES: Obama And The Facebook Crowd Connect In California

Men who choose a button-down shirt to wear with a suit and tie should consider a dressy fabric.

WSJ: Guide to Men's Shirt Collars: Which Styles Go With Which Occasions and Flatter the Face

Cho, 66, is the first to admit he prefers to wear not a suit and tie but a factory uniform, which he wore most days during his first 20 years at the company.

FORBES: The "Oof" Company

Not surprisingly jeans, shorts and singlets are not appropriate, with gentlemen encouraged to wear either a suit or a jacket and tie.

BBC: Kitted out for Royal Ascot