There are RULES and there are TIPS. Here are the RULES:

1. Use simple sentences. One subject, one action.
2. Use repetition for imperatives. Use repetition for emphasis. Use repetition for WARNINGS.
3. Avoid parentheses and anything else that can disrupt the reading.

Here are some helpful TIPS, based on the idea of a cookbook as the prototypical instruction set:

1. Physical steps should match logical steps. Sometimes a goal (e.g. completing part of a task) involves several actions. The immediate goal is to complete the "logical step," but whenever any actions that are part of the logical step (or, "physical steps") are left out of the instructions, the logical step becomes harder to complete. Example: calling for noodles or rice in a stir-fry recipe without mentioning they need to be pre-cooked.
2. Sometimes you just have to have a drawing! It's amazing how often engineering students and practitioners will try to describe with text alone concepts that have to be seen. This is especially important when referring to specific features of the object or system you're describing. It is important to be able to describe complex concepts with text alone -- but not in written instructions.

   NOTE: there are exceptions:

   • navigational directions, which require you to watch the road instead of reading a map;
   • telephone or online tech support, which requires you to give detailed graphics-free instructions;
   • graphics that are faxed or photocopied, and have become unreadable.
   The exceptions force you to write even more clearly than you might when you have graphics to lean on.

3. Introduce acronyms and jargon terms first, in the same way that a cookbook lists the ingredients before the recipe. Otherwise, terms your reader doesn't understand can stop or stall the whole procedure. Example: ever try to find a substitute for "tamarind paste?"
4. If you really have "ingredients," list them separately, and usually first. Once you give that list, there should be no mention of any ingredient not on the list. "Ingredients" may include more than "things" as well:
   • access to external information (e.g. manuals)
   • likelihood of unrelated external events, e.g.
     • actions of external agents -- those not actually involved in the instruction but who may be in the area at the time
     • passing of time (e.g. letting paint dry)
     • change of system state (e.g. paint drying)
5. Assemblies should come with exploded views. No examples here. :-)
6. Give the steps in the order they're performed. Readers assume that the stated order is the required order. If there is no particular order, say so. Example: the order in which spices are added to a sauce.
7. If any step is not required, say so. If any step is critical, say so, and say why. Example: the bread must rise before it goes in the oven.
8. If any step has to be performed at a certain time or within a certain duration, say so. Example: the recipe may give how long it's expected to take even before the ingredients are listed.
9. If any steps are hazardous or can lead to hazardous consequences, give a *warning*, preferably a highly-graphical one. Example: the risk of pulling over the soda machine when you shake it to try to get your can to come out. :-)

Example (may be humorous?)

1. Do not ascend the ladder unless you intend to slide down.
2. Once at the top of the slide you MUST descend down the slide. Failure to do so IN A TIMELY FASHION may result in your forced removal from the top of the slide.
3. Before beginning your slide, ensure that the prior slider has, indeed, dismounted.
4. When sliding, keep all appendages within the confines of the slide.
5. Do not use the rubber soles of your tennis shoes to stop yourself on the slide. This is for your safety, and that of those following you.
6. If you are travelling too fast to come to rest at the lip of the slide, warn others below by shouting "Whee!"
7. Upon your safe arrival at the botton of the slide, dismount immediately, as to allow sliders behind you a faster, more enjoyable, experience.

Assignments

Take THIS SET of sample instructions and rewrite them into a serious instruction set.

1. Always try to get someone to follow your instructions before you publish them. If someone who's not familiar at all with the procedure can follow it safely, all the better.
2. Keep the instructions handy for updates based on user feedback. Douglas Adams says "anyone who thinks they've developed something completely foolproof has underestimated the ingenuity of complete fools." Users can find ways not to understand instructions, even without your help.