The best way to apply for a visa is from the Nepalese diplomatic missions in your country. All foreign nationals, except Indian Citizens need visas to enter Nepal.
The other option is to obtain the visa from the Immigration office at the entry points of Nepal such as at TIA Airport.
The cost is US$ 40 (30 days) and US$ 25 (15 days).
Two copies of your passport photos are required on arrival & your passport must be valid for atleast 6 month, from your departure date.
The best season to visit Nepal is from March to May and September to December. However, some tourists prefer to visit Nepal in the lean season too because there are abundant choices in terms of accommodation and flight bookings can be done very easily.
June to August is best time to do treks in Upper Mustang, Dolpa in Nepal and Mt. Kailash in Tibet.
Yes, we advise you to get your personal travel insurance from your respective country, which includes a comprehensive helicopter rescue coverage.