When choosing a Tibetan trek, there are probably four factors to take into consideration: length of trek, cost, popularity among other trekkers and proximity to Kathmandu. However, it's hard to find one trek that will meet all of these criteria to your satisfaction.
The length of a trek really depends on how fast you walk or how long you need to spend to acclimatise. The cost also varies according to the season you decide to go to Nepal. This is directly related to the amount of other trekkers you will meet along the way. During the monsoons, you will probably be one of the very few tourists to trek anywhere; consequently most lodges will give you free accommodation and even a bargain for food. But in the busy months of October and April, you will hear more European languages spoken than Nepali, and might even have to race other trekkers for the best rooms. Finally, as for the proximity to Kathmandu, all treks are pretty much an inevitable long bus ride away, with the exception of Helambu.
The two treks I chose to do, after having considered all options, were the Helambu and Langtang, linking them via Goisakunda in August, peak monsoon season. However, since most people have less time at hand, I will only write in detail about the latter, which is also the most interesting of the two.
If you're not reaching Langtang through Helambu, you can approach the area by bus. Currently, there are three buses that connect Kathmandu to the Langtang National Park. They leave at 6.30, 7.00 and 7.30 am, cost 140 rupees (110 if you only go to Dunche) and, unfortunately, take anything from 10 to 15 hours. Before the town of Ramche, near the entrance to the park, the road has suffered a two-kilometre series of landslides, which will probably take years to repair at Nepali speed. This has partly interrupted the bus service. Thus, the bus drops everyone off at the beginning of the landslides and you have to walk across the dangerous two kilometres to catch another bus at the other end.
Eventually, when everyone and their belongings (anything from backpacks to heavy cement and live hens) have disembarked, walked across and taken back their seat in the new bus (most stand, though, since buses get VERY CROWDED), you finally proceed to and enter the Langtang National Park, just before the town of Dunche. You go through the last Army check-post and pay the one-thousand-rupee fee (you need to provide your passport number along with your personal data).
Once everyone is on the bus again (passengers can be left behind at any time, so make sure you hear the engine going and loud honks), you continue on and soon arrive in Dunche. Some people get off here for an extra trekking day, but it's pointless to stay in Dunche and better to continue onto Syabrubensi, a two-hour steep descent just at the real start of the Langtang trek. This is where all the villagers of the Langtang valley also spend the night. There are several hotels in Syabrubensi. A room costs 50 rupees, except for Hotel Buddha which, for 100 (you can bargain it down to 75, if empty), offers a hot shower. This can be the last luxury you might want to afford after a dirty, long and tiring bus ride.
Syabrubensi is not really an interesting town and only functions as the departing point for your trek. The day after, you descend towards the rivers down below (the Trisuli Bhote Kosi and Langtang Khola merge at Syabrubensi), pass a Police check-post, cross one steel suspension bridge over the Trisuli Bhote Kosi river, go through Old Syabru, cross another bridge over the Langtang Khola river, and finally commence your climb.
The trail is not very steep at first and it's just a little exciting walk through fly- and leech-infested weeds (even the popular marijuana plant grows naturally here, although it doesn't get you high at all). It does get more interesting after you reach Landslide Lodge, just past a big landslide on the Northern side of the river and a big waterfall along your trek (you might want to remove your shoes if you don't want to trek with wet feet for the rest of the day).
After Landslide Lodge, the trail starts a long, steep climb through thick and dark woods. You continue on the Southern bank of the river, pass the few lodges at Bamboo Lodge and, further up, cross another steel suspension bridge to do the final, perhaps steepest, climb along the Northern bank of the Langtang Khola.
It takes about six hours from Syabrubensi to Lama Hotel, what the town of Changtang is popularly called after the first hotel to have opened there. Most people stop in Changtang since this is where you find the largest selection of lodges. It's a very nice cluster of hotels near the river, immersed in the forest. However, you come across other lodges just before Changtang that are as nice. Or, if you walk fast, you can go further to Ghoda Tabela where you find other accommodation just two hours away.
If you stay in Changtang, a good place is Tibet Guest House for the food and hospitality of Karchun and her husband, Choesang. They have a very spacious kitchen with a clean stove. Make sure you try their Tibetan tea and ask whether she's got any apples to sell you (the town one hour above Changtang has apple orchards).
On the second day, after the 700-metre ascent of the previous one, you leave Changtang at 2470 metres and make your way up to the village of Langtang, at 3450 metres. The trail to the first settlement of Ghoda Tabela is very much like what you did for most of the previous day, climbing at times very steeply through tall trees and dense vegetation, passing numerous waterfalls, streams and some landslides.
After Ghoda Tabela, once you've gone through another Army check-post (this is what the Army seem to do best in Nepal, other than killing Maoists), the landscape gradually changes, the trees giving way to only flowers, bushes and weeds. The trail, with the exception of one steep climb 30 minutes past Ghoda Tabela, just before Thangshyap, is also a pleasant, gradual ascent and will be less tiring than the first day.
Langtang is a series of guesthouses before the actual village. Houses here are built in Tibetan style, like most you come across after that, with stone walls and bamboo roofs. Again, there are many hotels to choose from, but a homely option is Tibet Hotel, run by a young couple who have a small child. The owner speaks very good English and, other than enjoying the fresh cauliflower and carrots from his garden, ask to hear his Yeti stories and adventures of his first time in Kathmandu, which are surely entertaining!
To save one day, the final village of the trek (Kyanjin Gompa) is only two hours away, climbing only 400 metres to 3850. Otherwise, spend the night in Langtang and reach Kyanjin Gompa in the morning.
In Kyanjin Gompa, the best-located hotel is Hotel Monastery. Built on top of small hill, it overlooks all the other hotels down below, and it's right next to a small stony monastery with fine thangka paintings on the inside walls. The owner, Suppa Lama, will happily give you a good price if you plan to stay for a few nights. Make sure you try their buttery Sherpa soup and their boiled potatoes with a spicy dip, this last item not on the menu but very delicious and filling. Also, to get rid of any snotty cold, Suppa's wife has a miraculous powder that, snorted up your nostrils, surely works!
Depending on the season, you find cheese either in Kyanjin Gompa or Langtang. The cheese factory in Kyanjin Gompa was established by a Swiss man about 50 years ago, after having spent three years in the valley. Their "Swiss" cheese is very good and reasonably priced at 270 rupees/kilo. However, make sure you try their six-month-old, since it's much tastier than their three-month-old. You may have to buy a whole six-kilo cheese during the low season but, as more tourists make their way up, the cheese is cut in small portions and sold by the gram.
In October, after having spent the milder summer months in Kyanjin Gompa and the rest of the valley further East, all the cows and naks (the female of the yak) move to Langtang and below where it's warmer in winter. This is the reason why the factory in Kyanjin Gompa closes and the other one in Langtang then opens. This one too was established through foreign aid (Japanese) and makes fresh cheese, including Italian mozzarella.
More than the cheese and the monastery, Kyanjin Gompa is really about mountains, and this is where you will see and enjoy the Himalayan peaks at their best. The town is a good departing point for day walks. You can climb past the monastery up North to get right in the heart of the Langtang peak and the Lirung glacier. Another possibility is going up the peaks of Tsergo Ri or Yala Peak, at around 5000 metres, for fine views of all the snow-capped peaks around you. Additionally, you can follow the river up East through a trail that takes you to unpopulated areas, yak houses and views of all those other peaks that are not visible from Kyanjin Gompa.
You can expect to pay around 250 rupees/day during the low season, if you take two meals per day, eat local food (as opposed to try-outs of continental food) and stock-up with candy bars, biscuits and dried fruit from Kathmandu – these are excellent snacks when you're running low on energy.
This reason, plus the fact that there are very few tourists, is why it's good to trek during the monsoon months. Rain is not really the issue – it mostly rains in the evening or at night, and otherwise a good raincoat will do just fine. Actually, because of the frequent rain, you come across very lush vegetation and colourful flowers, as well as an abundance of streams, as opposed to a cold, dry, often heavily snowed landscape you can expect during the winter months.
Perhaps, the only drawback of this season is the clouds, which can surely obscure the view of the highest peaks for a good portion of your trek. However, sooner or later, you are sure to see and enjoy them, most likely in the early morning and when the wind blows from the East. And then, it will be a real treat for your eyes!
You need not to worry about bringing a sleeping bag, since all lodges have blankets for you to use (that saves space in your backpack for goodies). You might want to bring candles instead and, if you're not good walking in darkness, a torchlight since most lodges have toilets outside. Also, bring warm clothing for higher altitudes and a book to read.
As a final recommendation, try to stay at smaller lodges instead than those big ones like Lama Guest House in Changtang, Village View in Langtang and Yala Peak in Kyanjin Gompa. These, not only are mentioned in the Lonely Planet and thus already get a lot of tourists, but they are also the ones that always cater to groups with guides. Guides get up to 50% of what you spend at a lodge they take you to. If you hire a guide, make sure you establish at first that you will pick the hotel. However, you do not need a guide at all since the trail is very easy to find, and locals always go up and down and can give directions.
So, why Langtang? Because it's a short trek that will surely give you a good insight to life in the Himalayas. It's not only the mountain views that you will enjoy, but also the people that inhabit this region, of Buddhist religion and Tibetan descent, will definitely make an impact on your life as well. Their stories will certainly make you think twice next time you will complain about all the comforts and unnecessary privileges you enjoy back home.