Snip. I have learned, over the years, to clearly mark what they were for, what bit and template guide was used, etc.
For furniture makers/woodturners, equally important, if not more, is to date and sign every major piece of your work.
Oh, yeah. I have been doing that for many years. Everything I build gets the job number, which is assigned when the job comes in. That is only a partial clue though, because some big jobs don't get to me for a long time. The custom pieces are usually done last.
Then the name of the job itself, along with the date that I take it down to the floor from the blocks, followed by my scribble of an autograph, with a black marker.
What is really cool is getting to rework a project after many years and finding the original date/autograph on the back or inside, depending on what it was. We have re-made cabinets that were damaged by a water leak and find name and date from 10 years back or more sometimes.
This is a habit that started when we first started using a second cabinet carcass press. One of them was clamping slightly out of square, which became noticeable to the installers on long runs of uppers. Marking them with "who" assembled them would tell us if it ever happened again. Also, since the cabinets themselves are CNC cut, they have stickers identifying each part. Most of them are peeled off during assembly, but the ones on the backs and nailers are left on. They have all of the job name, room number, sequence number, etc too.