There is no right or wrong way to write an SOP. However, your company probably has a number of SOPs you can refer to for formatting guidelines, outlining how they prefer it done. If that's the case, use the pre-existing SOPs as a template. If not, you have a few options:   A simple steps format. This is for routine procedures that are short, have few possible outcomes, and are fair to the point. Apart from the necessary documentation and safety guidelines, it's really just a bullet list of simple sentences telling the reader what to do.  A hierarchical steps format. This is usually for long procedures -- ones with more than ten steps, involving a few decisions to make, clarification and terminology. This is usually a list of main steps all with substeps in a very particular order.   A flowchart format. If the procedure is more like a map with an almost infinite number of possible outcomes, a flowchart may be your best bet. This is the format you should opt for when results aren't always predictable. There are three main factors to take into account before writing your SOP:   Your audience's prior knowledge. Are they familiar with your organization and its procedures? Do they know the terminology? Your language needs to match the knowledge and investment of the reader.   Your audience's language abilities. Is there any chance people who don't speak your language will be "reading" your SOP? If this is an issue, it's a good idea to include lots of annotated pictures and diagrams.  The size of your audience. If multiple people at once are reading your SOP (those in different roles), you should format the document more like a conversation in a play: user 1 completes an action, followed by user 2, and so on and so forth. That way, each reader can see how he or she is an integral cog in the well-oiled machine. What it boils down to is this: Are you the best person to be writing this? Do you know what the process entails? How it could go wrong? How to make it safe? If not, you may be better off handing it over to someone else. A poorly-written -- or, what's more, inaccurate -- SOP will not only reduce productivity and lead to organizational failures, but it can also be unsafe and have adverse impacts on anything from your team to the environment. In short, it's not a risk you should take. If this is a project you've been assigned that you feel compelled (or obligated) to complete, don't shy away from asking those who complete the procedure on a daily basis for help. Conducting interviews is a normal part of any SOP-creating process. If you're writing or updating an SOP for a group of individuals that are familiar with protocol, terminology, etc., and just would benefit from a short and snappy SOP that's more like a checklist, you could just write it in short-form. Apart from basic purpose and relevant information (date, author, ID#, etc.), it's really just a short list of steps. When no details or clarification are needed, this is the way to go. What's obvious is that you have a procedure within your organization that keeps on getting repeated over and over and over. But is there a specific reason why this SOP is particularly useful? Does it need to stress safety? Compliance measures? Is it used for training or on a day-to-day basis? Here are a few reasons why your SOP is necessary to the success of your team:  To ensure compliance standards are met To maximize production requirements To ensure the procedure has no adverse impact on environment To ensure safety To ensure everything goes according to schedule To prevent failures in manufacturing To be used as training document If you know what your SOP should emphasize, it'll be easier to structure your writing around those points. It's also easier to see just how important your SOP is.
Choose your format. Consider your audience. Consider your knowledge. Decide between a short or long-form SOP. Keep your SOP purpose in mind.