Write short, crisp sentences describing the supporting evidence. Incorporate them under each major point in logical order. Try limiting most of your sentences to less than 12 words. Do not write a longer sentence unless you can do so skillfully. Short, crisp sentences that make a point are easier to write and read.
People write introductory and conclusion paragraphs differently.
If you normally have trouble getting started, then leave the introduction and conclusion for last. It is easier to set up your argument in the introduction after you have already put the body of the paper together. First paragraphs are where a sophisticated reader will decide whether or not to take you seriously. In the end, your conclusion should relate strongly to how you set things up in the introduction. Write topic sentences for each paragraph.