For any reference point on the Earth, the qibla is the direction to the Kaaba. Muslims are ordered to face this direction during prayer (qur’an 2:143-144). While it may appear to some non-Muslims that Muslims worship the Kaaba, the Kaaba is simply a focal point for prayer, in a similar fashion to the cross for Christians or the temple mount for Jews.

The earliest Muslims prayed towards Jerusalem. According to Islamic tradition, when Muhammad was praying in the Al-Qiblatain mosque (in medina), he was ordered by God to change the qibla direction from Jerusalem to Mecca and the Kaaba. Various theories are advanced as to the reason for the change. http://www.geocities.com/mutmainaa/mosque/qiblatain.html

Muslim groups in the United States differ as to how the qibla should be oriented – some believe that the direction should be calculated as a straight line drawn on a flat map, like the familiar mercator projection of the globe; others say that the direction is determined by the shortest line on the globe of the earth, or a great circle. At times this controversy has lead to heated disputes. Flat-map Muslims in the United States pray east and slightly south; great-circle Muslims face in a north-easterly direction. In both cases, the exact orientation will vary from city to city. http://www.americanscientist.org/template/AssetDetail/assetid/14679

Some Muslims carry qibla compasses that tell them which direction to face no matter where they are. This method requires one to align the north arrow with a particular point on the compass corresponding to one’s location. Once so aligned, one simply turns toward the direction indicated by the compass’s Qibla pointer, which is often in the shape of a minaret. “Qibla numbers” for various locations are listed in an accompanying booklet and also http://www.stanleylondon.com/qiblanumbers.htm indexed online.