How does one use the words 'dass' and 'denn' in German? Do they send the verbs to the end? Do they change the context of the sentence? Do they require a comma to be placed in the sentence?

"Denn" is a co-ordinating conjunction meaning "for" and introduces a main clause, so use main clause word order after "denn". "Daß" is a subordinating conjunction like "that". Always use subordinate clause word order after "daß". Unless used at the beginning of a sentence, the preceding clause should always end with a comma in the case of "daß". In the case of "denn", the normal rule for commas separating the co-ordinating conjuctions ("aber", "oder", "und") apply. If the subject of the sentences changes a comma is essential. I hope this isn't too opaque.

Examples.

Sie ist zu Hause geblieben denn sie war sehr, sehr müde und deprimiert.

Ich bin davon überzeugt, daß das Verbrechen selber begangen hat.