There will be a number of arguments in a piece of discursive writing. Using linking words effectively can help you achieve this. These words are usually used at the beginning of a new paragraph, but they can also be used to link ideas within a paragraph.

Same line of thoughtfurthermore, likewise, in addition, similarly, also, moreover - numbering your points (‘firstly’, ‘secondly’, etc) is a rather mechanical method of linking and is best avoided
Conclusion or summarythus, therefore, consequently, accordingly, in retrospect, hence, in conclusion, in brief, as a result
Definite statementwithout question, without doubt, unquestionably, absolutely
Contrasting ideayet, on the other hand, nevertheless, however, although, conversely, otherwise, on the contrary
Further examplesbecause, for instance, since, for example, so that, despite the fact that, accordingly, although, if, though, unless