I am sitting across a table from my sister-in-law, outside a small Italian restaurant, reading her a letter. As experiences go, it's toe-curling. I am telling her everything I'm grateful to her for. It's like a bad episode of Oprah. Surely us Brits aren't built for this stuff?

But according to Action for Happiness, little things like this can really improve our lives. The movement, founded by LSE professor Richard Layard and Dr Anthony Seldon, aims to create positive social change, and comes as the government prepares to publish findings this autumn on its proposed happiness index.

The movement's core idea is that we should all try to create more happiness. Or, to paraphrase the Dalai Lama, happiness doesn't just happen to you, you have to work at it. To this end, a list has been drawn up of 50 activities, from getting to know neighbours to unplugging from technology, that can make positive changes to our lives. But can they work? I spent a week finding out …

Being kind

According to the organisation, doing kind things for others strengthens our connection with them and builds trust – particularly with strangers – leading to happier communities. The acts can be large or small, but must be beyond the things you do regularly.

This is not hard. To my surprise, I am not overly kind. I'm polite, I'm friendly, I hold open doors, but my natural reserve prevents me from, say, mowing a neighbour's lawn.

So I step it up, offering to let someone queue-jump (he refuses), and trying to help a pair of lost tourists ("Nein danke, we're fine"). Finally – yes! – a couple struggles off a bus with a wheelchair and bag of shopping. I take a bag, give the woman my arm, and walk her to the wheelchair. I feel like Mother Teresa.

Give thanks

Next I must write down, every night, three things I'm grateful for. This, apparently, helps us to feel happier, healthier and more fulfilled – and less materialistic.

It turns out that I am a natural, scribbling down teenage things such as "amazing swim!", "gorgeous day!", "James McAvoy!". After a particularly bad day it makes me feel instantly more upbeat.

"This action helps us to reframe our perceptions of how our day is going," says Action for Happiness's director, Mark Williamson. "It's not about ignoring bad things, but asking, did anything good happen today? You can usually find something."

Being mindful

Meanwhile, I am trying to meditate. Boy, this is hard. I chose it for its supposed power to transform, through teaching us mindfulness – living in the present rather than dwelling on the past or worrying about the future – which in turn can make you more robust.

The meditation website, Headspace, instructs me to sit for 10 minutes each morning, focusing on my breath, observing my thoughts. At first, turning my mind away from work, worries, my to-do list and breakfast, is impossible.

"Everyone experiences this at first," Headspace's founder, Andy Puddicombe, reassures me. "People think you have to somehow switch off, but actually meditation is more about switching on, developing awareness. So don't let a wandering mind put you off."

And, sure enough, as the week progresses, I start to look forward to it. It gives me a calm but ready-for-anything feeling that's rather novel. I even try it when swimming. With a bit of extra effort, entire lengths go by unnoticed, and afterwards I feel not just physically exercised, but more clear-headed.

Write a letter

Another suggestion is that you should thank the people you're grateful to, and that the best way to do this is by writing a letter, then reading it to them.

My letter-reading day is looming. I've chosen my sister-in-law for several reasons but mainly because, although life is easier if you get on with your in-laws, there's no compunction to like, let alone love, them. But I do – she is like a sister, and I've never told her that.

According to Williamson, this will make us both happier, and has a knock-on effect – if we know others have valued something we've done, we are more likely to do it again. In fact, all happiness can be contagious. Research from the US suggests it can affect not just us, but our friends, their friends and even their friends.

Reading the letter makes me cringe. I do it quickly and perfunctorily. My sister-in-law stares into her lap so she doesn't meet my eye. I'd put a few weak jokes in there to diffuse the awkwardness. But afterwards she looks like she might cry. She tells me she is deeply touched, had no idea how much she means to me, and feels the same.

Better still, the rest of the night is spent discussing previously taboo subjects: a long-forgotten bust-up; how neither of us are exactly how we appear; what my mum says about me behind my back. It's refreshing to air feelings in a positive context, rather than after a fight, and I come away not only understanding her better but glowing with something indefinable – the sensation, perhaps, that I've done something really nice.