You can read this article if you are taking flight to Nepal for first time. http://nepflights.com/blog/5-things-you-should-know-if-you-are-flying-for-first-time-in-nepal/
If you are traveling to Nepal for first time, you might experience lots of unexpected things. I am not saying it will be always interesting but i hope you will feel different. One very obvious thing, If you are taking flight to Nepal, you will landed in Tribhuwan International Airport, the only international airport of Nepal till now. So you first city will be Kathmandu: capital city of Nepal, Beautiful destination, culture and heritage rich.
But what i am going to suggest might be different for you. Most if suggestion depend on the situation and purpose of traveling to Nepal.
You will first face the airport process which go not just you imagine. Everything looks like manual, queue, filling the papers. You have to painstakingly fill the form for immigration officer and wait in queue.
Most of the restaurant, hotels and other shopping shop take card payment but not everyplace. Specially when you travel on taxi they need cash. So it’s like compulsory to you have hand cash. You should know exchange rate is change everyday, there you can see lots of money exchange counters with different conversion rate. If you are going there, try to know first from internet so it will help you to bargain. But i suggest you first see the real trends from Central Bank of Nepal : http://nrb.org.np/
In case of emergency try to exchange little as you need.
When you get outside from Terminal, you can see lots of taxi and sometime even drivers bother to ask you for ride. They may try to overcharge, so first try to get the lowest cost as possible.
Still if you don’t get good response, walk down toward the main exit gate, you will see other taxis. They are easy to deal than others. I suggest you to go on taxi meter every time.
Nepal is having the problem of few hours loadshedding everyday. This might make you feel strange but don’t worry most of the place manage power backups. So while choosing hotel and restaurants, try to get if there is enough power backup.
Take off your shoes
Take off your shoes while entering a house especially in the local community as its considered very impolite if you don’t. If any of your friend invite you to his/her house you need to do this. But don’t worry about other place like Hotels and Apartment.
Always walk around a stupa or Hindu temple in a clockwise rotation because its part of both Hindu and Buddhist customs.
In Nepal people greet by saying Namaste with joining hands in front of you as this is the traditional. The good impression is to saying Namaste is it shows you have a basic understanding of Nepali culture which goes down very well.