duplicates and merging

Sooner or later in your family history research, you are going to discover that someone else has been working on your same line.  This may cause excitement ("that's the information I've been looking for!") or frustration ("All that time and effort for nothing!").
So, how do you discover duplicates?
It may be apparent when you add a new person, such as a child or spouse to a record.  A long list of possibilities will pop up in family search as "this person may already exist in our data base."  Seldom is there enough information at this point to confirm a match.  Usually, I go ahead and create a new person knowing I will have other opportunities to make a match and merge.
Once I have a name, place, and birth/death dates, I can submit the name for temple work.  At that time the system might alert you that possible duplicates exist which you must check out before submitting the name for temple work.
There are other times when duplicates will appear such as when attaching a record.  A little warning "!" will appear indicating that this record is already attached to someone else in the system.  They will give you the ID code and you can check to see if it is the same person or not.
Computers are not perfect at finding duplicates.  You must be the eyes and brains in this operation.  After merging a family, you may find that several researchers found the same children so you will need to go to each child and merge them.  Don't just delete them as you will lose the records and memories attached, not to mention the ordinances already completed.
After spending an entire evening researching back several generations, I discovered I was working on a duplicate line that had all the temple work completed.  My first reaction was "that was a waste of my time!"  Then I realized that I had made several important contributions: I had attached records, filled in more complete names and dates, found missing spouses and children, discovered parents.  If I spent hours researching a family and found save it be one name, what do you think my efforts would be worth to that one child whose name was found?
Everything you do is for a purpose.  You may be fine-tuning research skills, discovering new ways of doing things.
Do not fear merging data. (Most things can be undone.  If not, they will warn you beforehand.)  Be cautious in deleting information unless it is obviously an error or a duplicate.  Far better to spend an evening of your time discovering you have duplicate information than to do all the temple work for dozens of names only to find out someone else has already done it!  (That is called "fat" names and unfortunately far too many people were having their work done multiple times in many different parts of the world.  That is why this whole system of sharing information was created in the first place: to eliminate duplicating the work!)

Let's practice merging.  A ward member had two of his living sons listed twice.  He can't delete them., but he can merge them.  Here's how:
Copy the id number of one of your duplicate sons. Go to the other version of that son under the detail page. Look down the right side of the page for possible duplicates. The computer won't find any. Click the button at the bottom of that search that says merge by ID. Paste the ID number of the duplicate. A split screen will appear. Move everything you want to keep to the left side. Then click merge. Repeat for your other son. You should end up with two boys instead of 4. Let me know if you run into a snag during the process.