My understanding of the typical construction of a sentence/clause in German is that the 2nd position is occupied by a verb so
"Ich glaube das nicht."
"Das glaube ich nicht."
are both valid. However, certain words occupy the 0th position. The two examples which come to mind are "denn" and "aber."
"..., denn ich glaube das nicht."
Unless there's some rule that I am totally missing, does anyone know of a relatively comprehensive list to become familiar with?