On that subject, what software have you tested? I have worked with several over the last few years (not just in the sign industry) and my favorite seems to be Asana. Lately, we have been testing a very simplified shared spreadsheet with status and minimal job info and it has been pretty good. I like having the option of a full blown CRM, PLM, and task management system ready to roll out for scaling when the time comes, but as most of us know the big challenge is fitting the variety of jobs into the system. It's painful to justify paperwork and entry/tracking of two vinyl DOT numbers that are out the door in less time than in takes to make the invoice...
I've tried a couple task management programs and a couple other ones I can't remember, free trials only. If I had employees I can see using them. I have a receipt book I use for smaller jobs or I print a "walk in customer" invoice. Yes, can be a pain to record but I can't tell you how often someone wants a reprint and thank goodness I wrote down the vinyl color!
One thing I do use on my desktop is "Fences" - it's basically a folder but you can see everything in it. I have Artwork, Proof Out, In Production, On Order, On HOLD, Common Jobs, Personal, File. It helps greatly in keeping my files in order...but it's only good if I use it every day
(screenshots from Google)