[dba-SQLServer] deduplication

Is there a SQL syntax or method for identifying duplicate records based on
and automatically removing (or marking) the second and subsequent instances
of that record.
 
I am working with a database where there may be several records for the same
person.  Each record will have slightly different data in the record.  I
need to find all the records for a given person, remove or somehow flag the
"duplicate" records, and eventually "merge" the duplicate records together.

 
I know how to use groupby and count to find the dupes but I don't really
know how to then merge fields F through M from records 2,3 and 4 back into
fields F through M in record 1.  This is going to be an ongoing project so I
need to learn the methodology to get it done.  I can do it with recordsets
and code, but not with SQL, and given the large potential numbers of records
SQL would be my first choice.
 
John W. Colby
Colby Consulting
www.ColbyConsulting.com