If you haven't obtained your entry visa for Nepal before your arrival in Kathmandu, be prepared for a long, long wait in a chaotic, stuffy airport.
Wait times for a visa can be up to 3 hours.
You will need a passport size photo and US cash -- $25 for 15 days, $40 for 30 days, $100 for 100 days. The line ups are incredibly long, disorganized and people get angry and upset, especially if they have another flight to catch. The officials are unhelpful, bureaucratic and ill prepared to handle the large number of people arriving every day in Kathmandu.
It's the most chaotic airport terminal I have ever visited.
Even the lineups for those who have obtained a visa before arriving are long.
If you do have a flight to catch and are at risk of missing it, explain this to one of the staff wandering around to staple photos to application forms and she might escort you to the "Diplomatic, Special Visa" line for faster processing. It's still confusing, slow and they don't speak a lot of English, but you might get through faster and still be able to catch your flight.
By the way, if it's a domestic flight you need to catch, the domestic terminal is about a 10 minute walk (with a cart) to the right as you exit the International Terminal. Don't bother taking a taxi unless you have a lot of gear. It you do need a taxi, it should cost no more than 100 rupees.
The best advice is to apply for your visa before you leave home, if at all possible.
Note that in some countries, visas are only good for a limited period of time, so if you are on the road for an extended period, it may not be possible to apply for a visa in advance because it might expire by the time you are ready to visit that country.
Travel tip shared by Dan Cooper