Some good news if you're going on a trip to Nepal: The procedures are very simple and not too onerous at all. So there's no need to worry as you plan your trip.
NB. After the two powerful earthquakes that struck Nepal in April et May 2015, the country is slowly getting back on its feet. This article was written before the disaster.
In order to embark on a holiday in Nepal, first of all you must hold a passport that's valid for at least six months from the date you request your visa. You will need a visa before you can enter the country. For UK citizens, it costs £20 for a stay of 15 days, £35 for 30 days and £75 for 90 days.
For Irish citizens it costs €15, €35 and €75. Prices vary slightly for citizens other countries. Application information and prices are available on the internet. Look for the location of the Nepalese embassy in your country. In any case, if you request your visa before your departure, allow for a delay of at least two weeks.
No vaccinations are required to enter Nepalese territory. As a precaution it is a good idea to have them for yellow fever, typhoid, hepatitis A, rabies, Japanese encephalitis and meningitis A and C.
If you are thinking of hiring a car whilst you're there, don't forget to obtain an international driving licence before you leave.
To make life easier and save a little money, you can also request your visa at the border and at airports. A 15 day visa shouldn't cost more than $25 and for 30 days it's about $40$.
If you fall in love with the country you can extend your stay for up to five months in total. To do that, you need to go to the immigration office in Katmandu or Pokhara. Be careful during the procedure and firmly refuse to pay any imaginary taxes that police officers may ask for.
Be aware also that a visa doesn't allow you access to all areas of the country. Thus you need to ask for a special permit for certain treks. In Kanchenjunga, it costs about £6 per person per week. It's more expensive in the Manaslu region, where you need to spend about £45 per person per week. In the high Mustang area it's about £32 per person per day. Then if you decide to try to conquer Mount Everest it will cost you a trifling £12,000 (depending on exchange rates).