Before students can learn to use dependent subordinate clauses properly, they need to know what they are. Most dependent subordinate clauses begin with subordinate conjunctions, such as, "after," "although," "because," "once," "unless," "whether" and "while." Provide students with a list of subordinate conjunctions and ask them to memorize them. Teach students what a complete sentence is, and show them that dependent subordinate clauses are not complete sentences because they do not contain an independent subject and verb.
Once students know what a dependent subordinate clause is, they still need to be able to recognize one when they see one. Make a worksheet with a variety of sentences. Have students underline the dependent subordinate clause in each sentence. Make another worksheet with sentences containing a blank space where the subordinate conjunction should be. Have students fill it in themselves. Take up the worksheets as a class, and discuss common errors that many students made.
Students also should be able to add dependent subordinate clauses to existing sentences. Give students a worksheet with sentences containing only independent clauses, such as, "John walked slowly to school." Have students add their own dependent subordinate clause to provide additional information, such as, "because he had a test that he didn't want to write." Also, have students do the reverse by providing dependent subordinate clauses and asking them to add a dependent clause to each.
The ultimate test of mastery over clauses is whether students can use them properly in their own writing. Have students write a paragraph or a short story, depending on their grade level. Stipulate that their piece must contain a certain number of dependent subordinate clauses. Have students exchange their writing and underline dependent subordinate clauses in each other's work. Let students discuss in pairs whether they used the clauses properly.