I find that writing my notes in layout jargon (e.g. text_1 rather than the first paragraph) reduces the number of errors I find on the second pass. Much easier than having layout learn my language.
I probably wouldn't go this far, but recently one of the more senior layout people took a few minutes to explain points and picas to me. She also said that, from what she's seen, the capital letter in a font seems to be 2/3 of the point size in height and the lowercase letters will reduce to 1/3.
Here's her sketch, with charming floating I-dots:
On the rare occasions where I've needed exact measurements, our company has printed a variety of rulers out on a transparency so that you can take measurements from docs set at 100%.
[Update: apparently these are known here as acetates. Metonymy!]