Nothing shows both polish and utility like the nattily tucked pocket handkerchief or 'pocket square' in the breast pocket of a man's blazer, sport coat, or suit jacket.
Never, never, never should the pocket square be of the same pattern as your ties. You are not 'Reverend Ike.'
Look at the greatest dressers in history - Philadelphia socialite and diplomat Angier Biddle Duke, Sir Anthony Eden, Fred Astaire, the Duke of Windsor, John F. Kennedy, and Gary Cooper - they all sport the well placed pocket adornment.
You have a handkerchief, put it in your pocket.
You gotta have a pocket square, I think.
A pocket square must always - always - be white and a bit wild. If it is too prepared, it is tacky.
I tend to keep my suit look casual but I like a good pocket square. It can change the look of any suit and give it an 'old school' feel. My preference is to make the square unique - different from the tie and suit color, so it really pops.
I have four or five custom suits, including one that's velvet, and a gray one I wear onstage. It's wool.