On the ground or on the couch, social media provides an unprecedented opportunity to reach millennials, Shadi Rahimi says.

Social media offers news media the opportunity to reach young millennials, and to learn while doing do.

"Twitter is a very forgiving platform," says Shadi Rahimi of one of the three - with Facebook and YouTube - on which Al Jazeera has built its US news offshoot AJ+, becoming one of the world's top news publishers there.

Already, the outlet - which operates on social media only, without a website - has made a name for itself by getting out to cover events such as the Ferguson and Baltimore protests, but Rahimi says AJ+ has discovered it can also be of service, just Tweeting in front of the TV.

"If we're on the ground and tweeting, we get audience that grows by the minute, but we discovered that also happens when we're watching a live stream or TV and tweeting," she says. "When you think of where our young audience is, they're not watching TV but they are on Twitter and Facebook. Providing them with the service, we're catching them and we're catching even more people."

The channel also shares content from other sources, such as media organisations (which are fully credited) and citizen journalists and "ordinary people", where Storyful or direct contact is used for verification.

Understanding audience has been key to building a position for AJ+ said to be the second biggest news publisher in the world on Facebook and the ninth biggest publisher of video. "It's the audience every site in the US is seeking," she told a WAN-Ifra India audience in Mumbai.

A deputy producer for engagement, she says travelling light - with little more than iPhones to record and publish - helped them get close to the action, starting with Ferguson, the Missouri city to which she and a producer made three visits last year. Lately it has taken the same approach in Europe, reporting the refugee crisis.

"Everything we do is tailored to the platform, and we keep video short - never more than a minute-and-a-half for breaking news and seven minutes maximum for documentaries," she says.

Key on Facebook are the language used above a video, and the first three to five seconds of it, as a majority are watching on their phones. "If you catch them, you've got them... at least for the next three to five seconds," she adds ruefully of the notoriously fickle audience.

Social media does however, provide unprecedented opportunities to track audience. "It's amazing the data which is available, so we have audience strategy and data teams that analyse the way that people are viewing and reacting to our video," she says. "You have to win social media in order to win your next generation of audience - you cannot ignore that."

Shadi Rahimi, who moved to AJ+ from a role as a freelance journalist - during which she covered the 'Arab Spring' events of 2011 in Egypt - is used to working with a minimum of equipment, although in some cases, media producers have extra kit including shotgun and lav microphones, monopods and LED lights to improve quality.

In Ferguson, a decision was taken to report using only mobile phones. "The clips were shaky but this is what social media audiences love. They love to feel they are on the ground with you, watching the sort of video they shoot themselves," she says. "Entering the conversation as a news organisation, we did so in the same style as the activists and that way we got all of them to come to us."

Rahimi says the strategy is "all about engagement, not just putting the news out there, but getting the audience to engage with us and engage with the news itself." That means one-on-one conversations with members of the audience, asking them questions and responding to their comments, even to the extent of researching one and coming up with an answer.

"It's a very flat approach, rather than the media's standard top-down," she says. "We are a community member of our audience rather than speaking down to them as news used to do."

Understanding engagement brings a strategy for the form and length of video, trimming and tailoring for each specific audience. No-one knows what will go viral, but studies show it tends to be items which invoke joy or anger, calling for the "nugget of news" that will drive people to share, enabling them to break news or be seen as a source, or associate themselves with the content: "People won't share unless they want to align in some way, be happy or angry," she says.

Early in the history of the AJ+ channel, coverage of the Ferguson events "took over" the Twitter timeline for periods of eight to 12 hours, but sharing too much on Facebook is more likely to alienate their audience - some of which is international - with shares kept perhaps three hours apart and limited to a story and a couple of videos.

Live streaming - using apps such as NBC's Stringwire - is also fraught with potential problems, as it requires a strong data signal, not always available at events where crowds are involved. "If it's really jumpy, your audience just gets annoyed, so finding the right moment for it is important."

Shadi Rahimi urges keeping the service element foremost: "The experts say you should only be promoting yourself about ten per cent of the time, and the rest you should be providing a service - information and entertainment - to get and keep followers.

Consistency is also important - "don't live tweet once and then never again, but provide a regular service" - and experiment. "We've tried lots of things, and you shouldn't worry about making mistakes," she says. "Twitter is a very forgiving platform.

"Ultimately social media is a space that allows for innovation and it also provides amazing amounts of data about your audience, so it makes it really easy for you to be able to adjust based on the audience you have or the audience you want to have, or both.

• From a presentation to WAN-Ifra India Conference