How to tell jokes like a pro

"Why do giraffes have such long necks?" I ask a woman in her 80s outside King's Cross station in London.

I've been asked if I can try to perfect my joke-telling skills. So here I am, accosting strangers with a list of gags. I agreed to the challenge because jokes have never really been my thing. Telling a funny story? Sure. Taking the mickey out of my friends? Great. But this purest form of comedy, which so unashamedly screams "Laugh at me!" has always been a struggle.

So getting tips from the comedian Lucy Porter was a welcome offer.

We headed to the busy station so she could observe me telling jokes "cold", without any prior guidance. To put it mildly, it wasn't great. To put it accurately, it was excruciating and only one person laughed.

After the baptism of fire, Lucy and I sat down for a quick lesson, so she could indicate where my flaws are. Unsurprisingly, it's my manner. "First of all, you were unbelievably rigid, physically," she said, suggesting I should appear "confident and happy" while doing my comedy business. Second, I needed more variation in my voice and more belief in the funniness of the joke I'm telling: "If they trust that you're going to make them laugh, they will laugh," Lucy assured me.

Less encouragingly, she says telling punchline jokes is "probably the toughest kind of comedy to do. I wouldn't do what you're doing." It turns out people don't just laugh because they pity you – it actually has to be funny.

After our pep talk, I'm back by the station. "If I believe I'm funny, they will think I'm funny," I tell myself as I approach a man in purple denim who, based on that outfit, simply has to be up for a laugh.

I tell a joke involving a man in a grocery store. I do funny voices for each of the characters; my posture is relaxed; I am relaxed; the joke is funny. The man grimaces for a couple of seconds, says "very funny", and walks off.

My next attempts have mixed reactions. Some people really laugh, and some people really do not. I will admit it was a good feeling when people laughed: I was relieved, of course, but it is also satisfying to know a stranger thinks you are funny.

On top of that, I obtained some entirely infallible and comprehensive generalisations from the experiment that I will share with you: old people do not like poo jokes; young people like mean jokes; only people who know about Descartes will appreciate Descartes jokes; laughing hysterically immediately after your own joke does not guarantee that response in the other person.

Lucy taught me some useful things, mainly that delivery is almost all that matters. I also learned that joke telling is a lot harder than it seems. It's a real performance, which makes you very vulnerable, whether you are a professional comedian, or just with your friends telling jokes in the pub. Every joke-teller put themselves through a trial to make people smile.

I can safely say I won't be going up to people in the street to tell jokes again, but Lucy has taught me that if you think you're funny, the chances of other people agreeing are a lot higher.

Oh, and the giraffe punchline? "Because they have really smelly feet." It's how you tell 'em.

What I learned

Leah's top tips

1. Relax If you feel awkward, so will the other person

2. Vary your voice Monotone speech makes the joke boring

3. Signal the punchline A little pause adds to the suspense

4. If they don't laugh, give up Desperation isn't funny

5. Believe in the joke you are telling If you think it's funny, they are more likely to agree

Take it further

At a class

Try the one-hour beginner's comedy taster with a professional comedian at City Academy, central London. Learn the basics of a joke and find the 'funny you'.

On a course

Jill Edwards has taught comedians such as Jimmy Carr and Shazia Mirza. On the weekend workshop in Brighton, learn how to structure jokes, write funny material and polish performance skills.

At a festival

Not quite ready to take on Edinburgh? Fringe by the Sea, the coastal cousin of the comedy giant, runs open-mic nights throughout the 6-day festival in North Berwick, 4-10 August.