On Afghan culture
Believe it or not, Afghans once had an incredibly rich culture, combining ancient native custom with a pastiche of influences and refinements from around the world. "Once" was a thousand years ago. Studying it is fascinating as a matter of contrast to the modern day.
There have been a number of things over the last century at the very least that have trampled the Hell out of native culture in Afghanistan. Most recently, a few multidecade episodes of foreign invasion, literally uncountable displaced Afghans scattered among refugee camps on three continents, generation gaps big enough to drive a genocide through, and ongoing ethnic pogroms have stripped off anything that might have been left. Most importantly is the admittedly and proudly intentional dismemberment of Afghan culture through systematic and longstanding policies of the governments of Pakistan and Iran.
Looking at Afghan culture today and trying to find what it used to be is like looking at a runway model after half an hour in a sandstorm. One of the last tenacious remnants (the heavy duty eyeliner that refused to give up, perhaps) is Afghan tea culture.
There are rigid protocols, procedures, preferences, and varieties. Learning the nuances can take a lifetime if you're not raised in it. And unlike, say, Europe's High Tea or the Japan's Way of Tea, there are no books with which a dilettante can amuse themselves and others, or schools for the more enamored to attend.
To understand Afghan tea culture, one must first understand the Afghan culture of hospitality. A host has several and severe obligations, upon which rest status and pride. Suffice it to say, if you think a Jewish mother or an Italian grandmother are pushy, you've seen nothing until you've tried to fend off an Afghan armed with a pot of tea or plate of bread. In fact, Afghan hospitality is a lot like Afghan warfare: They don't ever stop until you've died or gone away.
The most absolutely destitute Afghan will borrow money from a loan shark and send their youngest directly to the market to put out tea and bread for a guest. A guest is anyone in their home who doesn't live there and hasn't just kicked the door in... And even in the second case, sometimes. I highly recommend you cruise through Pashtunwal to at least get a further understanding of melmastia.
So, you've somehow managed to end up in an Afghan's sphere of influence as a guest. Perhaps a business meeting with an NGO counterpart in Kabul. Perhaps a quiet call on a village elder in his guest house to discuss why they keep letting people store explosives in their granary. Maybe you've returned to the Korengal with a backpack and a tourist visa to meet with some old friends and see how things are going. Whatever the case, there is going to be tea.
On the varietals
There are several varieties and preparations of tea common in Afghanistan. Green tea is all pervasive. Black tea is fairly rare. If you're very lucky, you'll be served shidi chai, or milk tea.
Shidi chai is relatively expensive and time consuming to make. There are regional variations, but you can expect it to be very heavy on milk and very sweet. Sometimes made with green tea, sometimes with black. Sometimes with goat milk, sometimes with cow milk. Sometimes white sugar, sometimes brown sugar. There will be pieces of tea leaf swirling throughout. In any case, it's usually pretty delicious, and it's very easy to be a disgusting hog and blow through an entire pot of it pretty quickly. You'll want to take it easy for a couple of reasons, not least the fact that you will probably shit your face off if you drink too much of it without being acclimated.
Shidi chai is usually served from breakfast up until second prayer, and after last prayer; time periods roughly equating to before brunch and midnight snack, respectively. Though if it's winter time or your host is well-off, all bets are off.
At any other time of day, you will with almost utter certainty be dealing with green tea. Among many others, there is the ever present Lipton green in bags; Alokozai brand, also in bags, for those who can afford it; and most rare and highly treasured, a variety of whole leaf loose green tea with green cardamom pods, known as chai sabz. Chai sabz will be served with huge chunks of leaf and cardamom pod swirling throughout. Eat them if they happen into your mouth while drinking.
As a guest, by default your tea will be about 75% sugar by volume. This is easy enough to deal with if you don't like it that way: When tea is offered (more on that in a moment), simply request your tea trikh, or "bitter". Or, for "just a little sugar", ligh ligh shirin. In my experience, just a little in the mind of an Afghan host is still too much for most Western palates. Heaping sugar on guests is a remnant of when sugar was not nearly so cheap, and is a way for the host to show extra consideration. I drink mine trikh and nobody is offended; as long as they offer, you can decline without offense. Just like with ritual greetings in Afghanistan, the asking is what's important.
Along with the tea, whatever it may be, there is an absolute compulsion for food to be served. Even if it's something as simple as an individually wrapped candy placed on the saucer next to the teacup, a host must never be caught without sustenance to offer a guest.
It's common to keep a divided dish on hand, for guests, filled with the traditional assortment of unsalted roasted pistachios; Afghan raisins; walnuts; and some kind of small, toasted nut-like thing I never figured out the English name for. There is also usually a center compartment with a couple of nuqul (candied almonds) or pieces of wrapped candy in it.
A word on Afghan raisins: You will not believe that raisins can have so much flavor. They're made locally, from Afghan grapes. There are cultivars there that are unknown outside of the local areas in which they're grown, and would probably blow the minds of winemakers the world over. Afghanistan could probably make more money selling fruit and making wine than they can with opium poppies. Try two or three of the brightest raisins together with a walnut. Then, try to not eat the whole dish worth.
Depending on circumstances, you will be offered anything from a battered piece of candy, to a hank of bura dodei or "sugar bread"; all the way up to what I sometimes call this complete breakfast. A full breakfast, known as sahar chai or "morning tea", in Afghanistan would be shidi chai, naan, cream cheese, honey, several kinds of jam and/or fruit, white rice, fresh yogurt, and butter.
Lunch is usually the simplest meal of the day, ranging anywhere from tea and bread or the fancy version, shidi chai and bura dodei; to a kebab and some naan or perhaps a three-dish plate of meat, rice, and dal.
Dinner can be the same as lunch, but ranges up to overwhelming in terms of spread size. An affluent host serving a planned meal can get downright silly with the hospitality thing. I've personally been served a fifteen course dinner.
On being a guest
Regardless of the circumstances, as a guest there are a few rules to remember.
First: When you are outside your hotel room, barracks, bunker, or consulate, you are probably the guest. When you are in a home, shop, a workspace, an office, or even a park, you are the guest. If you're invited somewhere, you are the guest of the person who invited you and possibly the sub-guest of the person who invited them.
Second: as mentioned previously, the asking is what's important. The most common way to invite someone to sit for tea or food is not as a question, but as a statement - "You're drinking tea", or "You're eating food". You will be asked with bewildering frequency to drink tea, share food, or partake in whatever happens to be going on. A polite guest will either A) turn down the first request and then acquiesce based on the amount of insistence; or B) partake of an absolute token, such as when you're invited to share a lunch obviously meant for one.
If you're asked three times to partake, you had better at least go with option B.
Third: Compliment the victuals. If it's weak tea and crappy candy, find something nice to say. A favorite standby is "It feels so refreshing to take a break for tea," or in the winter time, "I wish I could stay indoors and drink tea with you all day! It's so cold out there, the hot tea is wonderful."
Lastly: Watch your portions. In general, drink as much tea as you think your kidneys can handle. Green tea is cheap and plentiful. Take it easy, though, with shidi chai or food, especially when you're not dealing with a rich Afghan. An American with a healthy appetite can go through a week's worth of food for the average Afghan in a sitting. When you feel done, it's not impolite to simply say "finished" or bas when the tea pot, ladle, or dish is inevitably thrust at you again. And again. And once more for good measure. Once you've taken tea or food, even a token, it's not impolite to refuse more. You can also put your hand over your teacup as you hold it if you're trying to finish and get the hell out, otherwise many people will just continue refilling without asking.
On the importance of taking tea
Bonding over tea and food is an immensely important part of Afghan culture. In fact, there's an expression in Afghanistan that translates roughly to "A hen that roosts here, and pecks there." It's the same as calling someone a fair weather friend, and specifically refers to someone who is polite and friendly but never eats with you. Such a person is seen as insincere and possibly duplicitous.
As a practical matter, you can expect that repeatedly turning someone down for tea because you're too busy, whether true or not, is going to result in some hard feelings regardless of any other circumstances. You'll need to find a way to make time to sit with the people you're going to be dealing with even peripherally, and have tea at least once in a while. The more important the person is to you, professionally or personally, the more often you should see them for tea. In reality, it would be more accurate to say the more important they are, the more often you should cave in to their invitations.
To the Western way of thinking, it's a huge waste of time. Well, it is true in the sense that you often don't accomplish much business during tea, either because it's purely a social call or because you're going to be bombarded with ridiculous pie in the sky stuff and depending on your position, naked flattery and office politics.
Keep in mind though; social relationships are the foundation of the way things are done in Afghanistan, both privately and in business. So, while sitting for tea may not get spreadsheets filled in or memos drafted, it's more likely that the person you're sitting with will decide to not be an intentional obstacle to you next time you need their participation or cooperation for something.
Another Afghan proverb to keep in mind - "A good friend is better than a good contract."