Here is a description of the procedure from Mauritius:
DEPARTMENT OF CIVIL AVIATION CIVIL AIRWORTHINESS REQUIREMENTS (MAURITIUS)
(a) COMPASS SWINGING AND DEVIATION COMPENSATION
This is a detailed procedure which is normally used for the purpose of compensating the compass to reduce residual deviation at all compass points to an acceptable level. The procedure involves observing the compass readings on different headings of the aircraft, calculating the deviation errors and determining coefficients, neutralizing the magnetic fields of the aircraft by adjustment of permanent-magnet compensator devices and recording any residual deviations on a deviation card.
(b) COMPASS CHECK SWING
This is a less detailed procedure which is used to compare current compass readings with those recorded on the existing deviation card. The compass check swing requires that compass readings be observed only on the four cardinal compass points.
Here is a guide from Hermanus Magnetic Observatory:
http://www.hmo.ac.za/Magnetic%20Navigation%20.htm
Here is a South African Air Force Compass Swing Record Sheet:
http://www.hmo.ac.za/Standard%20Comp...ing%20form.doc
The Hang Gliding Federation of Australia has a cute guide for swinging a Trike!
http://www.hgfa.asn.au/skysailor/Iss...ourcompass.htm