One of the most important parts of developing any system is writing procedures that are easy to read by all levels of staff and will actually be used. This is pretty much a no brainer but everybody seems to get it wrong.
First of all, ditch all of the information at the start that you don't need. If you need to put the "purpose" of the procedure then you need to look a little more closely at the people you have working for you. I have honestly seen a purchasing procedure with the first paragraph being "Purpose: The purpose of this procedure is to explain the purchasing process of the business" really Captain Obvious?
Things such as "scope", "preamble", "introduction", are just padding and are just more inclined to make an employee put it in the CBF basket. If a consultant writes a procedure for you that takes a whole page before even giving you any actual information is just padding out their time basically.
I've always found the best thing to have at the start of the procedure is a responsibilities matrix showing the tasks involved in the procedure and who is responsible for looking after them. This way an employee can quickly scan the matrix, see what they are responsible for and then go to that section to see what they need to do.
After that any definitions that you may need for common abbreviations unknown to new employees may be necessary but a full page of definitions is once again just padding.
Depending on the procedure it might not hurt to reference any relevant legislation or codes of practice that may apply to the task.
After all that it is a matter of going through the process step by step and documenting it in clear language and then auditing it to make sure it is correct.
Writing a procedure doesn't have to take 2 weeks and as long as you have someone who knows the task well to speak to you don't have to be an expert in it either. I have written procedures on how to maintain hydraulic front lifters without the slightest training in hydraulic mechanics because I researched the codes of practice and asked lots of questions.
If you would like any assistance writing procedures for your business please feel free to contact me firstname.lastname@example.org