Whether you're doing technical writing, writing course materials, or even writing some how-to article that doesn't seem at all related to either of these topics, you probably at some point will have to write a series of instructions. Maybe those instructions have to detail how to get somewhere, how to use a particular software feature, or how to do cook that delicious meal you made last night.

Writing good instructions isn't rocket science, unless you're writing something for aerospace engineers, but it does involve practice and a good eye for detail. In particular, you have to:

• Consider your audience: If the people you're writing for have probably never used this program before, don't skip any steps whatsoever. Every click of a button and every click of a dialog box tab needs to be included so you won't leave anyone lost and confused. On the other hand, if your audience probably uses this program every day, you can be a bit more loose with the steps.
• Consider the consequences: If it is absolutely imperative that people do things in the order you specify, and in the amount and methods you specify, then make that very clear. And again, don't miss a single detail. A certain family member likes to tell the story of the first time he made a microwave lasagna for his parents, and the instructions never said to boil the noodles first. So he didn't. Crunchy pasta noodles fortunately aren't lethal.
• Consider the task: Some tasks are just plain fussy. For example, there's a popular text editor UNIX system administrators like to use, and when you're in editing mode, every keystroke is important. You have to literally include every key the person has to press when explaining how to do something. 
• Action order and not speech flow order: It's common for people to say things like, "Click New in the File menu." However, that's not the order you're doing the action with. In your actions, you are opening the File menu and then you're clicking Open, so it's better to write something like, "Open the File menu and select New." 
• Be the reader: Typically I'll write instructions while actually going through the process myself, trying to capture every step along the way. Sometimes I'll look at the scenario and ponder what might confuse me if I was new to the process. Being easily confused, I can usually think of something. Then I try to ensure that the reader won't have that problem.

There are some fun exercises a lot of technical writing classes go through in order to practice these issues. Try writing instructions for the following, and pair up with a friend:

• Making a peanut butter and jelly sandwich.
• Making a paper airplane.
• Pretty much anything that seems to be a simple, common, every day task.

Now give the instructions to your friend. Tell them they're an alien who has never done or seen this task before. Now, have them try to do the task only with the knowledge given in your instructions. Observing this exercise can be a real eye-opener, not to mention good for a few laughs. Not to mention a few mangled attempts at paper airplanes.