Think "Dependent Scentence".
Fragments are incomplete sentences. Usually, fragments are pieces of sentences that have become disconnected from the main clause. One of the easiest ways to correct them is to remove the period between the fragment and the main clause. Other kinds of punctuation may be needed for the newly combined sentence.
Ex. Fragment: Leaving her team at a time when we needed her.
Possible Revision: Coach Dietz exemplified this behavior by walking off the field in the middle of a game, leaving her team at a time when we needed her.