After tailoring, denim is your trickiest buy. The exponential options in cut, colour and condition are testament to the fact that your 501s have more than a century under their oversized belt. Unfortunately, the well-woven diamonds are buried among bootcut rough.

In the jewel trade, experts deploy the six Cs – carat, cut, colour, clarity, confidence and certificate – to ensure that what glitters can be sold. So we’ve pinched a leaf from their book, to craft a sextet of checks your new denim needs to pass. Now there’ll be no more sniggers from Canadian tuxedo-clad shop assistants when you confuse selvedge and selvage.

1. Crest (AKA Choosing The Right Brand)

First step – set yourself a budget. That number dictates whether you’re looking at an artisan Japanese label (the Far East bulges with innovative denim manufacturers) or an American brand your mum recognises. Not that the latter means worse results; Levi’s, Wrangler and Lee earned reps clothing cowboys and that nous endures.

Every brand makes jeans, but specialists do it best. Saint Laurent denim may be on-trend this season, but you’ll still be wearing a pair of Denham jeans in a decade. For more outré styles, try Japan’s Evisu or Canadian oddballs Naked and Famous, who once built a pair of 32oz jeans that could stand up without legs in.

If your tastes are more classic then Edwin, Nudie and A.P.C. specialise in stripped-back styles, more a base layer for an outfit, not its statement piece. Sample widely to find your favourite. As with your tailor, once you’ve found a brand that fits perfectly, it’s a relationship for life.

NUDIE THIN FINN JEAN Organic Dry Twill - click to buy EVISU 2023 Stretch Skinny Fit Discharge Seagull Denim Jeans - click to buy Levi's 511 Eternal Day Selvedge Slim Raw Jeans - click to buy Denham Razor Comfort Mid Wash Jeans - click to buy A.P.C. PETIT NEW STANDARD SLIM-FIT DRY SELVEDGE JEANS - click to buy EDWIN ED-55 RELAXED TAPERED JEAN - click to buy

2. Construction (AKA Know Your Materials)

With denim, cost correlates to longevity. Cheap out and they’ll split quick, so spend as much as you can afford. For cost-per-wear, even spendy denim’s kept its blue-collar roots. America is its spiritual home, but for denimheads, the best fabric is Japanese. That’s because when US manufacturers junked their traditional looms in pursuit of efficiency, Japan stayed loyal to 1920s machines, which give less uniform results. And for jeans junkies, individuality is the game.

There are two main types of jeans: standard and selvedge (or selvage, in the States). The former is woven in industrial quantities on equally enormous machinery, and is perfectly serviceable. The latter is crafted on traditional shuttle looms and is marked out by stitching (often red) on the inside of a turn-up. As ever, that craftsmanship counts, since selvedge is mostly made in smaller batches, from better materials, and used by better manufacturers. That scarlet thread is a signature of quality.

3. Cut (AKA How You Like Your Silhouette)

Jeans originated as workwear, so were cut baggy enough to be comfortable without getting in the way. Their transition, courtesy of James Dean, into fashion, subjected denim to some ignominious silhouettes (flares are currently attempting an ill-advised comeback, while bootcuts are a 1990s staple you should leave there).

Slim-fits have dominated recently, but things are finally starting to loosen up. You may not be enamoured of the wide-leg styles ported from the streets of Tokyo (although we’d argue that you will be soon) but spray-on fits should also be swerved. The most versatile is a slim silhouette, which tapers below the knee to avoid excess fabric flapping round your calf. Invest there first, then experiment.

Denham Razor Slim-Fit

4. Colour (AKA Don’t Taste The Rainbow)

The coruscating shades of modern denim would make Levi Strauss weep. But then, so would seeing men pay four figures for an item he designed to go down mines. Dry his eyes and stick to denim’s core four washes: black, indigo, faded and, in the summer, white. Leave coruscating colours to the boybands.

Within that quartet, the darker your jeans, the smarter they are. And the easier they are to wear. Black goes with anything from a button-down to a crew neck. White treads a fine line between Pitti Peacock and the forgotten half of Wham!.

A.P.C. PETIT STANDARD SLIM-FIT WASHED-DENIM JEANS - click to buy ACNE STUDIOS ACE SLIM-FIT STRETCH-DENIM JEANS - click to buy Uniqlo Slim Fit Selvedge Jeans - click to buy Uniqlo Regular Fit Selvedge Jeans - click to buy

5. Complexion (AKA Look Closely At The Details)

Denim’s devil is in the details. Your dry selvedge can look fine from afar, until people notice your chafe-induced John Wayne waddle. Denim below 14oz will avoid that. Keep an eye out for contrast stitching and embellishments on the back pocket – fine out of the office, less so with a blazer and tie.

Distressing, especially, needs attention. The aim is to skip the two years transitioning from raw denim to personalised wear. Not look like you recreated Fargo’s woodchipper scene.

Keep nicks to a six-inch window above your knee, to avoid accidentally emulating Rick Owens’ manhood-flashing AW15 show. If in doubt, buy an unsullied pair and slice your own with a razor. Carefully.

Nudie Jeans

6. Cleaning (AKA Yes, You Will Have To Wash Them Eventually)

Most of the myths around cleaning denim are precisely that. But it’s true that the longer they avoid the machine, the better.

Raw denim – dark indigo jeans that haven’t been washed – lose dye where they crease. These ‘fades’ are the denimhead’s Holy Grail, personalised wear marks that give a history of how you’ve worn them. The spin cycle extracts this dye all-over, so your jeans fade everywhere at once.

Nudie Jeans New to Worn Raw Denim Jeans

Six months is the minimum you want to keep raw jeans out of the laundry basket (if they’re black or came pre-distressed, that’s less important). But because biology has no time for fashion, scents can tempt an early wash. Resist.

However, don’t believe the anonymous denim aficionado who keeps his in the freezer; sponge yours, or deploy Mr Black’s Denim Refresh for spot cleaning that kills odours, not your fades.