Write two independent clauses with relating subject matter. According to the Purdue Online Writing Lab (OWL), an independent clause is a complete sentence: it contains both a subject and a verb and it expresses a complete thought. Sample independent clauses: "The dog is cute," "The dog loves people," "The dog barks a lot."
Combine the two by placing a comma after the first clause and then inserting a coordinating conjunction before the second clause. For example, "The dog is cute, and the dog loves people." The Purdue OWL identifies seven coordinating conjunctions: "and," "but," "or," "nor," "for," "so" and "yet."
Use different conjunctions to imply different relationships between the two clauses. For example, if you want to signal contrast between the two clauses, use "but" or "yet," as in, "The dog is cute, but it barks a lot." If you want instead to suggest a causal relationship, use "so" or "for." This changes the compound sentence to, "The dog is cute, so he barks a lot," and the statement now implies that the dog's cuteness causes his barking.