An adage in a certain school of screenwriting holds that early in a film — maybe five or six minutes in — the writers ought to lay out the theme of the film, usually in a line of dialogue someone says to the protagonist. Sometimes the theme arrives slyly; sometimes it’s more obvious. For my money, “Sideways” introduces its theme with all the subtlety of a singing telegram. The protagonist, Miles, played with fierce melancholy by Paul Giamatti, has just picked up his bestie, Jack, played with jaunty himbo vibes by Thomas Haden Church. Jack wants to get excited about Miles’s unpublished novel. Miles won’t have it. “I’m not going to get hopes up, you know?” Miles says in minute seven. “I have stopped caring. The hell with it. I have stopped caring.”

If you’ve seen “Sideways,” you know this is a whopper. Miles cares too much. He gushes with opinions, none more staunch than his opinions on wine. His certainty about wine gives him refuge from his insecurities about work and money and aging and love. He embodies a certain sort of aesthete, the one who knows a subject deeply, and whose opinions become a shorthand for the rest of us — those who do our best to keep up, who aren’t sure which wine to pair with the steamed mussels, let alone know whether Miles’s bottle of Cheval Blanc 1961 has peaked.

Moments after Miles announces how little he cares, Jack cracks open a bottle of Pinot Noir and asks, “How come it’s white?” Miles’s reply points to why we’re stuck toting around received opinions like his: “Oh, Jesus. Don’t ask questions like that up in wine country. They’ll think you’re some kind of dumbshit, OK?”

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A guy this conflicted is fine to question. Likewise, other conventional wisdom around wine customs deserves scrutiny. Take the adage that fish must pair with white wines and red meat demands red wine, the first rule of thumb anyone learns about drinking wine. The axiom is easy to recall, occasionally correct, and yet so flawed as to be effectively useless at dinnertime. Not every piece of wine lore is false, but between insecure snobs and skittish wine drinkers, much of the most common advice about how to drink, choose, and treat wine should be taken with a cork-sized grain of salt. Take for instance…

All Merlot is bad, all Pinot is good

Yeah, on this, blame “Sideways.” The film combined three dangerous elements to torpedo the Merlot makers of the world: a career-defining performance from Giamatti, memorable writing (Rex Pickett’s novel led to director Alexander Payne and writer Jim Taylor winning the 2005 Oscar for Best Adapted Screenplay), and a nuclear-grade slander of an innocent grape. “If anyone orders Merlot, I’m leaving,” Miles barks before a double date. “I am not drinking any f*cking Merlot!” Those 13 words were all it took to sink Merlot sales in the years after the film came out. “Poor Merlot,” a California winemaker named Billy Dim told NPR in 2017. “Merlot is one of the best grapes on the planet and the movie did some damage to its reputation.”

Meanwhile, the film seems to have boosted real-life sales of Miles’s favorite grape. Miles champions Pinot, for which he says California’s cool nights are perfect. “Pinot’s a very thin-skinned grape,” he explains. “It doesn’t like constant heat or humidity. Very delicate.” Of course Miles identifies as a Pinot guy. And he helped to launch a generation of Pinot guys — not to mention countless bottles of overripe, absurdly alcoholic Pinot from the Golden State

ABC (Anything But Chardonnay)

Listen, even on its worst day, Chardonnay tastes fine. It’s among the world’s most widely cultivated varieties, a star in many celebrated blends, and a versatile enough grape that Chardonnays range from bright and buttery to tart and nutty. Anyone who proclaims themselves staunchly anti-Chardonnay is likely complaining less about the taste and more about the image. Perhaps that’s because Chardonnay has a rep as the afternoon drink of choice for women of a certain age; perhaps it’s because Chardonnay has a rep as a basic, unchallenging starter wine; perhaps the ABC crowd balks at overplayed oak (chip) notes. None of these justifies a hardline stance. People who still prefer not to be seen as a Chardonnay drinker can simply order a different wine by name, if indeed their posture is a matter of taste rather than perception. Quoth Miles again: “I like all varietals. I just don’t like the way they manipulate Chardonnay in California. Too much oak and secondary malolactic fermentation.” See? Even the pickiest wine drinker in film history can get down with a Chardonnay.

Holding a wine glass by the bowl heats the wine

When your body is fighting an infection, you may get a fever of a couple of degrees, maybe slightly more. This is a defense mechanism at work. Bacteria are very touchy organisms, weakened by even that slight uptick from your usual 98.6 degrees Fahrenheit. So sensitive are they to a spike of those two or three degrees, their defenses fall, and your immune system wipes them out. You, meanwhile, may feel lethargic for a weekend. Then, you bounce back. Those two degrees simply will not kill you. In fact, you may not even notice them at all.

But back to wine. Don’t be afraid of holding the bowl; you’re probably not going to hurt a thing. In fact, if you’re served a too-cold white, a bit of body heat might even help open it up a smidge.

Red wine should be served at room temperature

Every ostia in Rome would like a word. Nothing feels more decadent on a hot day than a chilled red. Get something with bright flavors and lighter texture, plunge it into an ice bucket or give it a time-out in the fridge, then enjoy it with lunch on some afternoon when you’ve broken a sweat. Even on a normal occasion, though, you want to serve your red a few degrees cooler than the room. And storing your reds at room temperature will hasten their decline.

Mulling wine makes any sense at all

People otherwise punctilious about the temperature and provenance of their wine decide to scald a pan of it. Not even orange peels, cloves, and a glug of brandy can elevate it to more than a holiday novelty, the liquid reply to fruit cake. The tradition of mulling wine dates back to a time before most wine was reliably good. Now wine is good. You’ll enjoy it as is.

Natural wine doesn’t give you headaches

Nice try — a few people might be sensitive to sulfites, but for most folks, the headachy ingredient in wine is ethanol. The rules for avoiding hangovers from pét nat or orange wine are the same as avoiding hangovers from a Three Buck Chuck. Drink water, eat food, go easy. (And preferably don’t drink wine that tastes like stable sweepings.)

Fruity wines are too sweet

This is true only for legitimately sweet wines. Wine from later-harvest grapes will generally be richer in sugars, and a winemaker might lean into the sugar to make fruit notes taste like candy. But most fruit flavors aren’t sugar-specific. American palates have been conditioned by years of artificial flavors, food coloring, and high-fructose corn syrup. Uncork a bottle of a dry fruit wine and contemplate the lightning-and-the-lightning-bug difference between a fresh strawberry and a strawberry milkshake.

Champagne is only for weddings and New Year’s

Champagne has been typecast as a wine for fancy parties. If you knew nothing about Champagne, you might try a glass — maybe peachy, almondy, or toasty; definitely bubbly and enervating — and determine it pairs optimally with lazy Sunday brunch, among friends, at their apartment, where they play Rod Stewart records, and you stealthily pet their dog under the table with your toes.

All wine is better aged

The cliché that something is “aging like a fine wine” contains a key clue: that word “fine.” Being made of organic compounds, wines are prone to breaking down. That supposedly headache-free natural wine doesn’t want to sit on a shelf for more than a few months at most. Reds last longer than whites and usually do appreciate a bit of aging, as a rule, but neither is guaranteed to last longer than a year or three, let alone improve beyond that window, especially when kept outside of a wine cellar. For most wines the best move is to open them as soon as friends come over to watch Wimbledon or to play Settlers of Catan or to burn old branches in the fire pit. Some big event, in other words.

Wines with dessert should be sweet

Nothing against a zaftig port after dinner or a flirty Lambrusco after brunch — a shot of sweetness carries the joy of a meal back to real life. But why stack sweet on sweeter? Wine can complement a dessert without a sugar overload. Give a dry Syrah a chance to match the tannins in a chocolate bar.

Blends aren’t “real” wine

Far from being mutts, they’re more like designer dog breeds — a sign of someone who knows what they’re doing trying to put together the best qualities of two (or more) different grapes. But what’s more, trace any single grape’s lineage and you’ll find that humans cultivated them across centuries for different tastes, higher yields, and better resilience to weather and to pests. Life is melange. Enjoy that Grenache-Mourvèdre-Syrah labradoodle without apology.

The darker the rosé, the sweeter it is

Back to people (Americans) equating fruit and fruit colors with sugar. Rosé isn’t actually sweet, in general. In the United States, many people’s first experience with it might be a glass of Barefoot, which is sweet. A richer pink hue may give you the sensation of fun and indulgence, leading you to associate it with sugar, but that’s just one part of your brain messing with the other parts of your brain, a common pitfall of having a brain at all.

A glass of wine is whatever fits into the glass

A can of beer is a cinch as a single serving. A bottle of wine invites a bit of interpretation. Your 750-milliliter bottle contains five pours each of 5 ounces, the standard serving at most bars and restaurants, and an amount that tends to align with the lowest, widest part of the bowl of a red wine glass. On Netflix’s spoofy dark comedy, “The Woman in the House Across the Street from the Girl in the Window,” the protagonist, Anna, played by Kristen Bell, prefers the frankly mesmerizing full-bottle serving. After one floodlike pour of red, she leans over to slurp off the quivering meniscus off her glass; in another episode, she pours a glass to the brim and, while on speaker with her therapist, sets her phone as a lid across the top so she can carry the glass (and a second open bottle) without a spill. This strikes the viewer as funny because it is absurd! Note: It should strike the viewer as absurd.