Help them to prepare their computer hardware for the turn of the century. Review their software to be sure it is ready. Be sure to include networking software and all application and utility programs. Identify external systems from which you obtain important data, whether by electronic or paper means. Help your clients to identify all their machinery that have computer chips.
Computers are pervasive.
If a machine contains a chip, find out if it uses calendar dates. Work with them to make sure those machines are ready. There are several ways to accomplish this, not all satisfactorily. Ideally, the system will store and use four digit years. Some systems cannot accommodate 4-digit years, and will use other methods that are less reliable or are subject to other limitations.