Get in Pakistan
Almost all nationalities require visas. These are usually easier to obtain in your home country, though recently the individual missions around the world have been given more authority to issue visas without checking in with Islamabad, which should help in getting applications turned around quicker.
Recently a list of 24 “Tourist Friendly Countries” (TFC) was announced that are eligible for one month visas on arrival if they travel through a designated/authorized  tour operator who will assume responsibility for them while in the country. Any extensions on this type of visa must also be done through the tour operator. They include: Austria, Belgium, Canada, China, Denmark, Finland, France, Germany, Greece, Iceland, Italy, Japan, South Korea, Luxembourg, Malaysia, Netherlands, Norway, Portugal, Singapore, Spain, Sweden, Thailand, UK and USA.
Nationals of most other countries (and those not wanting to travel with a tour operator and group) need to apply in advance for a visa, which are usually issued for 30-90 days depending on nationality and where you apply. Double-entries are sometimes given, but be clear and persistent when applying that you need this.
A handful of countries are issued visas on arrival: Iceland, Maldives and Zambia for 3 months, Hong Kong, Nepal and Samoa for 1 month, while Tonga and Trinidad and Tobago nationals can stay for an unlimited amount of time.
Nationals of Israel are not allowed entry as it is not recognized as a nation by Pakistan. Despite much online information to the contrary, Israeli stamps and visas would usually pose no problems for entry into Pakistan, though you may be subject to more stringent questioning by immigration officers.
Indian nationals can apply for 30 day tourist visas but must travel in a group through an authorized tour operator. Visitor visas to meet relatives or friends are more easy to obtain, and come with some restrictions. Religious visas are granted for groups of 10 or more for 15 days.
Nationals of Afghanistan are refused entry if their passports or tickets show evidence of transit or boarding in India.
Holders of Taiwan passports are refused entry except in airport transit.
Business visas are now being issued for up to 5 years, multiple entry, as soon as 24 hours before arrival.
The Pakistan Consulate in Istanbul does not issue visas unless you are a resident of Turkey, although it may be possible in Ankara.
The consulate in Zahedan in Iran no longer issues visas, head for the embassy in Tehran.
The High Commission for Pakistan in New Delhi issues visas with varying degrees of difficulty, taking at least 1 day (and sometimes several) to process the application. Applications are only accepted in the mornings from around 9-11AM. Arrive early and expect the process to take a few hours, and possibly a few return visits. Window 5 is for foreign tourist and business visas (under the big white sign).
People of Pakistani origin living overseas are granted 5 year multiple entry visas (along with their spouses), good for single stays of up to 1 year. Visas aren’t required at all if they are holding a Pakistan Origin Card (POC) or a National Identity Card for Overseas Pakistanis (NICOP).
Karachi, Lahore, and Islamabad are the main gateways to Pakistan by air. However, there are 134 airfields in Pakistan. Six other international airports are in Quetta,Gawadar, Peshawar, Sialkot, Multan, Rahim Yar Khan and Faisalabad.
Jinnah International Airport in Karachi  is served by many international airlines, including Air Arabia, Air China, Biman Bangladesh Airlines, Cathy Pacific, Etihad, Emirates, Flydubai, GMG Airlines, Gulf, Qatar Airways, Saudi Arabian Airlines, SriLankan Airlines, Iran Air, Iraqi Airways, Malaysia Airlines, Oman Air, Thai Airways , and Turkish Airlines . It’s also the main hub of the national carrier “PIA”and 2 private airlines (Air Blue and Shaheen Air).
Allama Iqbal International Airport in Lahore  has been completely renovated with a new terminal for international arrivals and departures. Many airlines are currently operating to the airport including Emirates, Etihad Airways, Qatar Airways, Gulf Air, Pakistan International (PIA), Saudi Arabian Airlines, Thai Airways, Kuwait Airways, Oman Air, Uzbekistan Airways and two private airlines from Pakistan.
Benazir Bhutto International Airport (Islamabad International Airport) is currently in review to be expanded and modernized to meet the needs of the future passenger numbers as demand for air travel has increased dramatically. There are many airlines operating into Islamabad including many of the above with Ariana Afghan Airlines, Kam Air, Kyrgystan and China Southern Airlines. The only problem is that the airport is also used by Government officials as well as arrivals from foreign diplomats so the airport may shut down as security is increased so flights are delayed. Despite the no-smoking signs, smokers puff way freely in the departure lounge.
Whatever airport you arrive (or even depart), airport staff are certain to demand a bribe, especially from foreigners. Beware of anyone who insists on helping you- they won’t be so friendly when demanding you pay them. Furthermore, there is NO special airport tax due at check-in, despite what your check-in clerk might tell you.
Pakistan has train links with India and Iran, though none of these trains are the fastest or most practical way to enter Pakistan. Should speed be a priority it is better to take the bus, or if you are really in a hurry, to fly, however the trains are sights in their own right. Nowadays Pakistan Railways is going through recession. The number of trains has been lessened and trains don’t usually reach the destinations in time.
The Samjhauta Express runs on Tuesdays and Fridays between Delhi and Lahore via the Attari/Wagah border crossing. This is the most common option chosen by travellers, however, tourists should be aware that after recent terrorist attacks on the train, which caused many a casualty and strained relationships between the two neighbors, it is strongly advised that you take taxis or buses to and from the border instead.
The Thar Express runs from Bhagat ki Kothi in the Indian state of Rajasthan to Karachi in Pakistan’s Sindh province. This route restarted in February 2006 after 40 years out of service, but is not currently open to foreign tourists.
From Iran: There is only one link, from Zahedan to Quetta.
From ancient times people have been travelling through Pakistan using the Grand Trunk Road and the Silk Road that run through Pakistan and into the Indian subcontinent. It’s a rewarding but time consuming way to see this part of the world. New highways have been developed and the country is due for an expansion in its highway network. A world-class motorway connects the cities of Peshawar, Islamabad, Lahore, and Faisalabad.
From China: Pakistan is connected to China by the Karakoram Highway, a modern feat of engineering that traverses a remarkably scenic route through the Karakoram and Himalayan mountains. Plans are in place for this highway to be expanded from its current width of 10m to 30m as a result of the increase in trade traffic due to Gwader port opening.
The Khyber Pass connects Peshawar to Jalalabad and Kabul and requires an armed escort and a permit to travel through the tribal regions between Peshawar and the border. Onward travel from the border to Kabul is of questionable safety, check the current situation locally.
The Bolan Pass connects Quetta to Kandahar and is considered very dangerous. This route is not currently open to foreign tourists, and is only open to locals and aid workers.
From India: While there is international service running from Delhi to Lahore it is just as fast, much more flexible, and much cheaper to take the journey by stringing together local transport and crossing the border on foot. As of October 2009, the bus was Rs. 1500. The journey details can be found here: http://dtc.nic.in/lahorebus.htm. You cannot buy the ticket on the spot, rather you will need to show up a few days before at Delhi Gate with photocopies of your Pakistani and Indian visas. The bus leaves at 6 a.m. but you will need to be at Delhi Gate at 4 a.m. to check in for it.
From China: You can take a bus from Kashgar over the Karakoram Highway to Pakistan.
From Iran: Via the Mijva border in Iran which is half an hours drive from Zahedan. The Pakistani border town is called Taftan and has facilities of immigration, customs, hotels etc.