Lets take example of Clone Contact.
First we need to create n:1 relationship on Contact record:
Then we need to configure mappings:
Now let us put this field on the form navigation and lookup on Contact form:
Once you click Add New on Cloned contacts:
You see, all fields are copied which were configured. Fill and save:
Notice that source contact record is traceable through lookup(above the map). Happy cloning and hope it helps!