As a practicing entertainment lawyer, based in Los Angeles for nearly 40 years, Donaldson serves clients that include writers, directors, producers and actors. He has chaired the entertainment division of the Beverly Hills Bar Association, and is general counsel to the Independent Feature Project/West and the International Documentary Association.In 1992, he started teaching negotiating skills at the Entertainment Division of the UCLA Extension Program. The UCLA classes led to his writing Negotiating for Dummies, which has sold almost 150,000 copies and has been translated into nine languages. It is also available as a book on tape. In 1998, Donaldson was asked to teach negotiating skills to a large engineering company that led to a corporate-wide training program and speaking and training events at companies around the world. He is a popular speaker on the subject of copyright, film and negotiating. He has spoken at the Cannes Film Festival, Seattle Film Festival, Palm Springs and Vancouver Film Festivals.

He has lectured and/or participated as a panelist for many organizations including U.C.L.A. Extension, University of Houston, University of California, Davis (in Los Angeles), Montgomery Watson University, Colorado, California Lawyers for the Arts, The Independent Feature Project/West, International Documentary Association, The Los Angeles Independent Film Festival, The Sedona Conference, Arizona, Sundance Film Festival, Women in Film, Los Angeles, The Writers Guild Foundation and Cigga Hotels in Milan, Italy. Additionally, he has provided testimony as an expert witness in various entertainment lawsuits.