I would have to know the version of SQL to know how to answer this.
For 2008+, you have CDC.
For SQL prior to that, they probably wouldn't like my answer, but I would make the schema identical to the original table, adding a column(s) to the original schema if needed to support the logging.
This allows me to use all existing code and procs on the logging table, and/or to UNION ALL the two tables in such code/procs.
SQL DBA,SQL Server MVP(07, 08, 09) Prosecutor James Blackburn, in closing argument in the Fatal Vision murders trial:
If in the future, you should cry a tear, cry one for them [the murder victims]. If in the future, you should say a prayer, say one for them. And if in the future, you should light a candle, light one for them.