Let’s start with the most basic guidelines. If you are wearing a leather belt, it should match your leather shoes, if you are wearing them. Black shoes should be paired with a black belt, brown with brown and tan with tan.
The shades need not match exactly, but they must be close. The brown may be a little paler or a little darker, but it should not be able to be described as tan.
The texture need not match exactly either. The belt can be crocodile, ostrich or brogued. Indeed, a belt that matches the shoes exactly (both black crocodile, for example) smacks of artifice. Somehow it suggests you are all crocodile skin underneath, and only these two bits are peaking out.
Suede belts and woven leather belts are naturally more casual, and that should be reflected in the suit or outfit they go with – linen suits, odd jackets, outfits without ties. But again, colours should be similar.
Brightly or unusually coloured belts can work well, particularly as one pop of colour on an otherwise plain outfit. However, the colour of the shoes and belt should always be different enough to be a real contrast.
Brown is not an effective contrast with black or tan. Try primaries – reds, yellows – with black shoes, as you would with socks. And more muted colours with brown – oranges, greens – again as you might with socks.
The belt should not be too wide or too narrow. The easiest way to gauge whether it is either of these is to compare it to the width of the belt loops it will go through. Jeans have wider loops and should have wider belts. They can also be heavier, to reflect the material. Worsted wools should have sleaker, slimmer belts. But again the width of the loops is your best guide.
The buckle should be obvious, at least with a suit. Slim, discrete and silver in colour (unless you wear much gold elsewhere). No logos.
Ribbon belts can work well, particularly with summer outfits (again, matching the weight of the belt to the weight of the material it ties together). Best not to combine them with every other preppy accessory, though.
Ties as belts may have been a favourite of Fred Astaire but they are hard to pull off with elegance. If he had started wearing neckties around his waist before he was universally considered stylish, I would bet a chunk of money that it would have seemed artificial.
Next week, the follow-up question: whether to wear a belt at all. You lucky things you.