Database – Migration from Windows 1252 to UTF-8 character set

I'm considering migrating my database (Oracle) from Windows 1252 to UTF-8 by doing the following:

  • export all data (backup)
  • Shorten all tables
  • run alter database character set
  • Import data back

Is there a way to determine before the migration whether characters need to be lost or manually adjusted?

  • If so, how?
  • If not, how can you prevent characters from being lost during migration?