Recognize a subordinate conjunction when you see one. DEFINE IT!
SUB. CON IS THE WORD THAT IS PART OF THE SUB. CLAUSE.
The subordinate conjunction has two jobs.
First, it provides a necessary transition between the two ideas in the sentence. This transition will indicate a time, place, or cause and effect relationship.
The second job of the subordinate conjunction is to reduce the importance of one clause so that a reader understands which of the two ideas is more important.
The more important idea belongs in the main clause, the less important in the clause introduced by the subordinate conjunction.
AFTER ONCE UNTIL WHILE WHETHER WHERE THAT UNLESS ALTHOUGH BECOME BEFORE IF SINCE