A key piece of advice many writers either do not ever get or don’t believe is that it’s not necessary to write introductions first or to write conclusions last. Just because the introduction appears first and the conclusion appears last doesn’t mean they have to be written that way. Here’s a really tired metaphor to help explain: just because you walk into a building through the door doesn’t mean the door was built first. The foundation went in first, even though you rarely if ever see that part. And lots of imperfections in the foundation and the walls were covered up before you even moved in, so you can’t see those either unless you look closely.

Introductions

Even though a nearly infinite number of topics and arrangements is possible in English prose, introductions generally follow one of several patterns. If you’re writing a children’s story, you’d probably start with “once upon a time” or something similar. If you’re writing a research article in biomechanical engineering, you’d probably start with a statement about how previous research has examined the problem of loading soldiers with daypacks on various surfaces, including sand, concrete, and railroad ballast. These examples are poles apart, but their introductions share very similar purposes: they orient their imagined readers to the topic, time, and place.

In working toward the overall goal of orienting readers, introductions may

• Provide background about a topic.
  
• Locate readers in a specific time and/or place.
  
• Start with a compelling quotation or statistic—something concrete.
  
• Include an ethical appeal, with which you (explicitly or implicitly) show that you’ve done your homework and are credible.
  
• Articulate a main claim/thesis.
  
• Lay out the stakes for the piece of writing—that is, why the reader should
  bother reading on.
  

The following video addresses how to do several of these things, starting with the very first sentence of your introduction.

Conclusions

Conclusions usually

• Summarize the argument (especially in longer pieces of writing)
  
• “Bookend” a story that started in the introduction
  
• Include an emotional appeal, with which you (explicitly or implicitly) connect the “logic” of the argument to a more passionate reason intended to sway the reader
  
• Issue a call to action
  

Ideally, a conclusion will work in tandem with an introduction, having some kind of “call back” element to remind your reader of the powerful opening you provided. Additional advice for conclusions is found in the following video.