When the University of California at Los Angeles (UCLA) ended a $3-billion campaign in December, the effort was known as a success not only because of its large goal, but also because of the high participation by alumni. Three out of every 10 alumni made a donation, accounting for 22 percent of the total take. Now the institution faces the question of how to keep alumni engaged and interested until the next big drive. Keith E. Brant, executive director of the UCLA Alumni Association, says the marketing plan his organization follows is rather simple: constant communication via e-mail, a Web site, regional events, and a quarterly alumni magazine.