Certain phrases should set off alarm bells for every traveller. "Special menu" is one of them. "Good price", another. And most people should know by now that "I just want to practise my English" is a worldwide code for "I just want to take your money".
There's another, too: "Tea ceremony" - such a lovely sounding thing that it's easy to get sucked into. How could something involving the pouring of tea be used against an innocent tourist?
But tea ceremonies are fraught with danger. Wander the streets of central Beijing for a few hours and you'll soon figure that out. Every second stranger keeps offering to treat you to a tea ceremony. Surely, no one's that friendly.
These amazing offers invariably lead to some very average tea and a bill that looks like an international telephone number. It's a trick for first-time players; anything with the word "ceremony" in it is going to end up costing you a bomb.
So when the guy on the street corner in Lalibela offered to take me to a "coffee ceremony", I was smart enough to say no. The whole thing looked dodgy. He was perched on a stool outside a small house, clearly bored, throwing out the hopeful offer like a fisherman with his last cast of the day.
In Ethiopia, coffee is the beverage of choice. The drink originated here - along with, well, mankind - and it's a passion that remains. It's drunk black and strong - a thick, sweetened syrup.
I'd enjoyed plenty of cups of the stuff during my stay in the country but I'd never been invited to a ceremony and I knew the score if I was: average cup of coffee, ridiculous price.
"Hey man, you want to come inside?" the guy called from his perch, his dark face hidden by the shadow of the porch. "We can have a coffee ceremony."
I went to shake my head but something stopped me. I looked around. Lalibela, a town in central Ethiopia, doesn't have a lot going for it. It's home to rock-hewn churches that are truly amazing but once you've seen them, you've seen Lalibela. And I'd seen them.
All that was left for me to do was wander aimlessly around dusty streets trying to take in sights that just weren't there. So I made a call. I knew something was afoot with this coffee business but what else was I going to do? Fight off the shoeshine kids who wanted to buff my thongs? Maybe it would be worth getting ripped off just to get away from them.
"Yeah, OK," I said to the figure in the shade. "Let's do it."
He smiled one of those warm African smiles, then beckoned me into the wooden doorway. "See, my mother has already started," he said, indicating the woman just inside the doorway who was roasting what looked like coffee beans on a small fire. Suddenly, things had got interesting. They weren't going to make a ceremony out of serving me the coffee, I realised. The ceremony was in preparing it. From scratch.
The guy's name was Johannis, he said, and he'd lived in Lalibela his whole life. The two of us sat on wooden stools on the bare concrete floor and watched his mother prepare the drinks. First, the beans were roasted on a small pan while Johannis and I talked about Lalibela. Then the beans were crushed with a mortar and pestle while Johannis and I talked about football.
Next, the grounds were put in a clay pot of water, which was then set on the fire while Johannis and I talked about - well, football still. Johannis's mother laid out some cups on the floor before letting the pot cool, then reheating it again and finally pulling it off the fire and pouring small, thick shots into the cups.
"We drink three cups," Johannis said, passing me one and taking one for himself, while a sister appeared from another room, gave me a curious glance, then took a cup for herself.
I took a sip. It was like a caffeinated slap in the face. But a good one. More was to come, of course. The pot was boiled again, the cups refilled. Another slap. The pot was boiled again, the cups refilled once more with what was by now a jet-black sludge. Yet another slap.
It was fantastic - the coffee, the company, the fact I'd taken a chance, gone against my instincts and found myself in the middle of an ancient tradition. But the moment of truth had arrived.
"So," I said, turning to Johannis. "How much do I pay for this?"
Johannis looked confused. "Pay? For this? Nothing. You are our guest. I invite you in. It's nothing."
Just when you think you know it all.