Identify the independent clause. An independent clause has its own subject and verb; It is often referred to as a "simple sentence." For example, "he went to the store" is an independent clause ("he" is the subject and "went" is the verb) with a prepositional statement ("to the store") describing the direction of the action.
Determine the dependent clause. Note that dependent clauses can have a subject and verb, but they do not express a complete thought by themselves. In the previous example, if you wanted to modify the independent clause with a description of previous action, that would be a dependent clause.
Create a subordinate conjunction that best fits the sentence. For example, to describe previous action, we can say "He went to the store after going home," with "after" linking the independent clause with the dependent clause "going home."