I highly recommend you diligently identify and mark work pieces during the process of building a project. This is particularly important with a project that has numerous parts, or several parts that are nearly the same size.
There have been projects in my past that contained parts that were within 1/2-inch , 1/4-inch, and even 1/8-inch of each other. With dimensions that close, it’s REAL easy to grab the wrong part, slap some glue on, and attach it. It’s even easier to do this at the end of a work session, which is REAL interesting when you get back to the project the next day…
After I mark a measurement I like to go ahead and write the length as well as the part name BEFORE I make the cut. I often make several measurement marks on various parts at a time, so this really helps me.
Note in the above photo that I’ve marked an “X” on the waste side of the cut. I also don’t always use the “V” symbol to mark the line, and I use a .9 mm mechanical pencil rather than a carpenter’s pencil. Call me a rebel. I find the .9 mm lead works just fine on most lumber I use for interior projects. However, I do use a carpenter’s pencil and “V” on exterior lumber.