As a matter of habit, if I have a name like Judith, I would first run the name as given, then run it again with just the first two or three letters (ju__, jud__, etc.)  This would pick up any variations like Judy, Judi and so forth.  As far as a name beginning with a hard "C" like Carl or Catherine, I wouldn't run the "K" variation unless I knew it was one of their a/k/a's. 

When in doubt, I try to cover all my bases, however I think it would be almost impossible to run all possible variants of a name.

Hope this helps.

Regards,
Scott Perry