When I design a database, and local standards permit, I include both a surrogate primary key and audit columns on every table. 

A surrogate primary key is a system-generated integer that increments by one with each new row inserted.  Most DBMSs make it easy to add surrogate keys.  Oracle uses a construct called a Sequence, SQL Server calls its variant an Identity. 

The audit columns I like to include are these, shown with their SQL Server datatypes:  CreationDatetime (datetime), UpdateDatetime (datetime), CreationUserId (varchar (30)), and UpdateUserid (varchar (30)).  Most DBMS’s offer the ability to update columns like these with either default values or triggers.