One thing to watch for going forward is that sometimes the system will try to add someone as a "new person" (e.g., from a census record) who actually is in the tree, but the merge/add function does not recognize that. Always double check to see whether a name is being added as "new" so you can catch it at the front end - that's likely how some of your duplicates crept in. Don't forget the "merge duplicate" function to take care of this. Also, check the "list of all people" to make sure they really are duplicates - depending on what view you are in (pedigree, family, etc.) sometimes people who have multiple relationships may be displayed more than once - if they are "true" duplicates, you will see them in the "list of all people" and can address through the merge function, or delete, as necessary.