What's format? _ This is the layout of your document, where you decide the key order of the components (or chapters) of your standard. So for a user guide this might be; Contents Page, Product Introduction, Product Photo, Full User Guide, Quick Reference Guide, Copyright Statement, and Disclaimer. You can add as much or as little detail to each section as you feel necessary.
Why create one? _ "Re_inventing the wheel", is no fun. If you work for a single organisation it's likely that your templates could last a long, long time with no need to go back to the design board every time you are asked to create a new manual or user guide. When you work for yourself it's a great way to show clients that you have the skills they are looking for without breaking any confidentiality clauses with your existing clients, and with just a little bit of luck they'll adopt your method of working so you can continue to recycle your past efforts too.