I've heard that the acronym in a sefer usually appears in the sefer in its full form somewhere before the acronym does, and in many cases I find this, but sometimes I do not, and cannot figure out the acronym, and others fail to know also. How do you know what it means? Is there a dictionary or way to figure out from the text?
There is a sefer called Otzar Roshei Teivos - see it here and there is an older sefer with the same name that I can't find online, but probably your average Jewish book store would be able to get it for you. (Asuming you aren't needing to look these up when near a computer and want a small sefer for reference. The older sefer is smaller than the one I linked.)