Use a comma when the dependent clause has a subordinating conjunction and is located before the independent clause. Never use a comma with a dependent clause. When it introduces a list. None of the above. Non restrictive clauses begin with which and are not essential to meaning.
Restrictive clauses begin with that and are essential to meaning.
That introduces the main clause. Which introduces one of less importance. Always use that . Use that in the subject, and use which in the predicate. If the dependent clause is non restrictive, use a comma.