The Turner Construction Co. has begun work on The Pavilion, $4 million, three-level retail, restaurant and performing arts complex inside the Old Post Office building at 12th Street and Pennsylvania Avenue NW. The 60,000-square-foot Pavilion will house 50 stores clustered around a skylit "cortile" with a performance area at one end for day and night entertainment. The Pavilion is scheduled for occupancy in July . . . No doubt keyed to those who have made New Year's resolutions having to do with self-improvement, a number of area real estate-related organizations are offering educational activities this month. The Commercial Industrial Institutional Council of Greater Washington is sponsoring a conference on "1983 Commercial and Industrial Real Estate Investment Opportunities" this Tuesday at the National Housing Center, 15th and M Streets NW. Panelists will speak on a vaiety of trends in real estate investing. Information: 966-8665 . . . The Apartment and Office Building Association of Metropolitan Washington is putting on a one-day seminar Wednesday on "Office Automation and Telecommunications: What Will the Impact Be on the Office Building Industry?" The seminar will be at the Capital Hilton. The fee is $75. Information: call the AOBA, 289-1717 . . . The Associated Builders and Contractors of Metropolitan Washington is offering two construction-related courses: a 25-hour certificate course of basic instruction in blueprint reading, two days a week, starting this Tuesday and running for five weeks, and 25-hours of in-depth training for first- and second-level field supervisors. This course will be two days a week, Monday and Wednesday, starting Jan. 17 . . . Rufus S. Lusk and Son, Inc., has a new publication: a directory of every office building in the District. The directory, which will be updated yearly, gives such data as the building's legal description, zoning, owner, manager, land area, etc. A subscription is $395.