A standard operating procedure (SOP) describes how a recurring task should be done so it's done the same way, safely and correctly, every time. Most organisations have plenty of them. Far fewer can say whether anyone follows them.
The reason is usually format: a long document in a shared drive, written for an audit rather than for the person doing the work, with no way to tell whether it was used.
Write for the person doing the work
Start with who does the task and where. A technician on a plant floor needs short, ordered steps they can follow on a phone, not a ten-page document. Each step should be one action, start with a verb, and say what 'done' looks like.
Put the why next to the steps where it matters. People skip steps they don't understand the reason for.
Give every step an owner
Many SOPs span several people: an operator, a supervisor, a quality check. If the document doesn't say who does each step, the handoffs are where the procedure breaks. Name the role responsible for each step and what they hand to the next person.
Turn the SOP into something you run, not something you read
The most reliable way to get an SOP followed is to make it the way the work is done: each step appears for the right person at the right time, they sign it off when it's complete, and the next step opens automatically. The SOP and the record of whether it was followed become the same thing.
Critical steps can require evidence: a photo, a reading, a file. That's not about distrust; it gives the person doing the work a simple way to show it was done properly.
Review it using real data
Once SOPs are run rather than read, you can see which steps take longest, which ones run late and where work gets stuck. That's what should drive revisions: not a calendar reminder to review the document, but evidence of where the procedure doesn't match reality.