I don't necessarily subscribe to the .001" accuracy in woodworking espoused in some of the threads floating around here lately (particularly when a 4" wide board cut this morning at 65 degree/70% rh may well be a different width tomorrow afternoon when it's 95/95), but with wood getting more expensive by the day, it does pay to develop a method/philosophy of measuring, marking, layout and cutting that can get you "consistency" in the dimensioning of your parts ... which is what you should be shooting for when things have to go together as a whole.
On the methodology side, no amount of precision measuring will get you this needed consistency like the "batch" cutting/routing of parts, and the meticulous and consistent "referencing" of faces and edges to fences and cutting surfaces when machining/cutting ... particularly for a "production run" of multiple pieces in a small shop environment.
On the measuring side, I find myself going back repeatedly to the following tools for obtaining this necessary consistency, to the point that I even keep these, and like items, on a large plastic TV tray, lined with a non-skid rubber mat, so I can move them en masse around the shop as I need them:
Incra rule set (with the Bend rule the most used)
Sliding bevel square
With the above (and paying particular attention to maintaining reference edges), careful layout, marking and subsequent machine setup can be done with enough consistency to carry you from part 1 to part 101 with confidence, regardless of how many zero's of precision you put behind the period.
FWIW/YMMV, etc. ...