The French call them "consultants", in Italy they provide the commento tecnico, while in Scandinavia they're known as "expert commentators". Ostensibly, co-commentators are employed for their inside knowledge but, more often than not, they appear to be masters in the art of stating the bleeding obvious.
There's not much chance of you becoming a co-commentator if you don't have a regional accent and haven't had a journeyman career in and around the top flight. However, if you do possess the relevant qualifications, you may be interested in a step-by-step guide to your new career. These instructions will prepare you for any scenario or eventuality that requires your verbal intervention. What to say, how to say it and what not to say - it's all here.
Firstly, you're allowed to rely on clichés. You're not the experienced, slick media professional who's sat alongside you in the gantry. You can refer to an untidy challenge as "six and two threes" (if you're feeling adventurous) or suggest a player has "if anything, hit that too well" as the ball rockets over the bar.
All slow-motion replays are your territory. It's your job to confirm if the shot got a nick on its way through or if the goalkeeper did, in fact, get fingertips to it. Committing to a call before you see the replay is done at your own risk; if the replay proves you wrong, you'll need to awkwardly dig your heels in and refuse to concede defeat. The most dignified way of doing this is to admit some slight wrongdoing, but not enough to warrant a penalty/free-kick. Minimal contact? A coming-together? Nothing in it. After a while, you'll be oblivious to just how annoying this is for your viewers.
Offside decisions? If it's close, but you can actually tell whether it's offside or not, just say it's "borderline" or "touch and go". Don't use the visual tools at your disposal to decide one way or the other - that's not what the viewers want at all. What about that tackle, then? Clumsy more than anything. Don't forget the "more than anything" suffix here - no-one will prompt you to expand on what that "anything" actually is, lest you slander the player by mentioning exactly what it was that his tackle wasn't. While the game flows, it is the co-commentator's responsibility to keep an eye on any injured players and provide updates on their freedom of movement, on a vague scale ranging from "gingerly" to "much better now".
"...for me." Keep that ready for really desperate moments where you've been made to look stupid, but want to at least spare your fellow commentator from ridicule. I mean, it's a game of opinions, right? Don't worry too much about research, though. Sky Sports regular Alan Smith, for example, relies on a watertight formula of size + nationality to demonstrate his knowledge of the top players, be they big Belgians or little Spaniards.
Keep it light-hearted when appropriate. Make jokes about your own playing career, your lax attitude to training, or the commentator's playing ability. Or his age -go on, joke about how he'll be able to remember that far back when he mentions something that happened a long time ago! But avoid the temptation of Lawrensonesque over-quipping - this isn't Come Dine With Me.
Right, ten minutes in - which team has made the brighter start? It's the question on everybody's lips. If you can't work it out, just say they're "cancelling each other out" so far. Or the markedly creepier-sounding "feeling each other out". Have the bookies' favourites "got going yet"? "Not getting going" is easy to spot - they need to have failed to open the scoring. 20 minutes is the magic benchmark - if the underdog hasn't conceded in this all-important window, everything is going to be fine. Except you've shifted the goalposts for them - now they need to get to half-time. Speaking of which, you must become an amateur psychologist just before the break and judge which manager will be the happier of the two.
Sometimes, the most important statistic isn't in the top left-hand corner of our screens. When you're really struggling for an angle, up will pop the possession stats for the preceding 5-10 minutes. "Look at that!" you can exclaim, as we all do just that. Tell us whether that's what we could have expected or not. Later on, we'll see the epic two-part drama of the shots/shots on target statistics. The sheer tension as we wait to see how many of those 12 shots actually troubled the goalkeeper. A player shoots over the bar - he was leaning back. They always are.
Around five times a game, you'll be called upon to offer us The Bigger Picture as the commentator nips away to the loo. Halfway through the first half, on the stroke of half-time, the start of the second period, on the hour mark, and in the dying moments - you'll need to sum up what you've seen so far. Has it been a classic? Has one manager asked his team for "more of the same" in this second 45? As the time ticks on, will the other manager be thinking of a change? You can slide your way in to your observation, as the play enters a lull, with a wistful sigh that informs the viewer that you're about to offer your lengthy views on the action so far.
Do not describe players as short or slow - that's rude. They're "not the tallest" or "not the quickest". Why on earth co-commentators feel the need to shield the (obviously otherwise unsuspecting) public from the physical deficiencies of footballers is beyond comprehension. Is it some sort of PFA membership-inspired solidarity? Is it in fact a well-disguised challenge to Usain Bolt or the world's tallest man, Turkish part-time farmer Sultan Kösen, to take up football? Does Kösen have a good touch for a big man?
Congratulations, you're now a fully-trained peer of the Andy Townsends, Jim Beglins, Gerry Armstrongs, Davie Provans and Alan Smiths of this world. You're a combination of amateur comedian, psychoanalyst, anatomist and ex-footballer.
Perhaps it's not the easiest job in the world after all.