Get in Afghanistan
Most visitors need to apply for a visa in advance, and are often easier to obtain than you might expect. See the Afghanistan Foreign Ministry’s visa webpage .
Kabul International Airport (IATA: KBL) in Kabul is the main entry point to the country. In late 2008, the barely functioning old terminal was refurbished and is now being used for domestic flights, while the brand new Japanese-constructed terminal is up and running and fielding international flights.
The national carrier, Ariana Afghan Airlines , is flying with a small fleet of about 14 Airbuses and Boeings (plus Antonovs). They have daily flights from Dubai, and periodic flights from Frankfurt, Islamabad, Delhi, Istanbul, Baku and Tehran. Ariana is particularly bad at keeping to schedules, flights can be cancelled or delayed without notice.
A better option is the independent operator Kam Air , which has twice daily flights from Dubai, twice weekly flights from Delhi and weekly flight from Almaty, Istanbul and Mashad. Some of the flights on the Dubai to Kabul route stop in Herat if you’d prefer to enter the country there. Pamir Airways  is a new private airline that offers daily flights between Kabul and Dubai ($330 inbound, $210 outbound), some stopping in Herat. Safi Air also provides flights between Dubai and Kabul. They are the only safety accredited airline in Afghanistan. Safi is the only Afghan airline allowed to fly into Europe and has direct flights to Frankfurt, Germany. The service is good and planes are sound. Staff are professional.
Air Arabia  flies 4 times per week from Sharjah – however they have currently suspended operations. Pakistan International Airlines (PIA)  flies 4 times per week from Islamabad and 1 time per week from Peshawar to Kabul. Another route in may be via through Tehran or Mashad in Iran. Iran Air  has periodic flights from Tehran to Kabul. Air India  operates six flights a week from Delhi to Kabul. Spicejet, an Indian low-cost carrier flies three times to Kabul directly from Delhi (Tue, Thu, Sat). Turkish Airlines also began flights between Kabul and Istanbul in 2011.
Flights to other cities such as Mazar-e Sharif may be available if you can hook up with the charter company PACTEC  however seating is very limited.
Travel Warning WARNING The famous Khyber Pass is currently closed to anyone except Afghans or Pakistanis. Some travel blogs/forums claim that hiding in a vehicle and bribing the border guards works, but doing so is very risky and could lead to imprisonment. Even more risky, however, is the threat from Taliban near the pass, who have been known to kill/kidnap Westerners. You are strongly discouraged from passing through the Khyber Pass. (May 2009)
Torkham Gate in 2012, the busiest border crossing between Afghanistan and neighboring Khyber Pakhtunkhwa in Pakistan.
There are a number of roads into Afghanistan:
From Peshawar, Pakistan via the Khyber Pass to Jalalabad, in the East. The Torkham Gate serves as the border crossing, there is heavy presence of U.S. and Afghan National Security Forces (ANSF) on the Afghan side.
From Quetta, Pakistan to Kandahar, in the South.
From Mashad, Iran to Herat, in the West.
From Uzbekistan to Mazar-e Sharif, in the North.
From Tajikistan to Kunduz, in the North-West.
As of mid-2009, none of these routes can be considered safe. The Torkham and the Quetta to Kandahar routes are particularly dangerous.
Buses run regularly between Jalalabad and Peshawar, Pakistan. Also, between Herat and Mashad, Iran. Buses of both countries are thoroughly checked by border police for possible drugs or weapons, so expect delays.