WARNING: Non-Muslims are strictly prohibited from entering the city of Mecca. The penalty is deportation from the country. Documentation will be checked upon entry and anyone not showing proof of being Muslim will be denied entry. As a solitary exception, the Mecca bus terminal outside city limits is open to all.
The government of Saudi Arabia issues special visas for those making the pilgrimage. Most pilgrims opt to use a specialist travel agency, which will handle the considerable paperwork for them, but detailed information on the strict requirements is available at the Ministry of Hajj (http://www.hajinformation.com/). As usual in Saudi Arabia, women must travel together with a male guardian Mahram, unless they are over 45, travelling with a group and have their guardian's signed consent.
Visas are assigned to countries on a quota basis according to the number of Muslims they have. Recently, those who have previously been to Mecca have had additional restrictions placed on their entry, in an effort to discourage overcrowding while still accommodating those who have not yet made the pilgrimage. If the applicant was not born a Muslim, they must present a certificate testifying so, which has been notarized by an Islamic center. Usually your mosque will be able to arrange this or at least point the way.
By car
There is an excellent modern multi-lane highway from Jeddah. During the Hajj pilgrimage season it is jammed with buses full of pilgrims. At any other time, traffic is extremely light for the size of the road.
A few miles outside Mecca, there is a cutoff referred to as the "Christian bypass". Turn along this highway to drive another 50 miles out of the way to reach the lovely mountain town of Taif. Taif, at 5000 feet elevation, was the former summer palace of the Saudi Kings. If you remain on the main highway, there is a police checkpoint just after the exit, where non-Muslims are kept out of the holy city.
By bus
SAPTCO runs services to Mecca from throughout the country, although most pilgrims arrive on privately chartered buses from Jeddah. There are two terminals: the main terminal outside city limits is open to all, but the city center terminal at the Haram al Sharif, used mainly by buses to Jeddah, is restricted to Muslims only.
By plane
Jeddah is the gateway to Mecca. The Hajj Terminal at King Abdulaziz International Airport IATA: JED, used only for the Hajj, is served mostly by charter flights, although there are some scheduled services. During Umrah, scheduled services use the airport's other terminals.