This Sunday, the men of Hollywood will tread the Oscars red carpet under the watchful eye of the world, decked out in the sharpest black tie their stylists could rustle up at not-so-short notice. 

But for those of us without the world's top designers on speed dial, what are the guidelines of black tie and how to wear a tuxedo?

Here are five basic rules to stick to if you want to be the best-dressed man in the room at whichever swanky party you're invited to next: