Can't figure out what BZAW stands for? Here's some help with theological abbreviations.
If you are trying to decipher an abbreviation in a footnote in a book, please remember to look in the front of the book for a list of abbreviations! If the book has an index of authors cited, check it. The first reference in a book to a given work sometimes includes more detail than subsequent footnotes.
The SBL Handbook of Style for Ancient Near Eastern, Biblical, and Early Christian Studies lists abbreviations for primary sources, journals, reference works, and monographic series. It covers the core theological literature and is the best guide for a newbie. Buy a copy if you are serious about research. But many of the lists below are more comprehensive in their specialized areas. See also this searchable SBL abbreviation list.
Internationales Abkürzungsverzeichnis für Theologie und Grenzgebiete : Zeitschriften, Serien, Lexika, Quellenwerke mit bibliographischen Angaben = International Glossary of Abbreviations for Theology and Related Subjects : Periodicals, Series, Encyclopaedias, Sources with Bibliographical Notes. Abbreviated IATG. This is the most comprehensive list of theological journals and monographic series, but it does NOT include abbreviations for primary sources. Note IATG is divided into two halves: first half sorted by abbreviation, second half sorted by full title. Start with the first half. IATG uses European style abbreviations which may not exactly match the abbreviation you are seeking (e.g., JThS European style = JTS US style) so let your eye wander over the page. If you find a possible match, go to the second half of IATG and see if the year and volume number of the citation match that publication. A volume and year match means you probably have the right title for the abbreviation.
Most periodical indexes list journal abbreviations. So one way to decipher an abbreviation is to determine from the context of the abbreviation what field the work is in (e.g., theology, classics, rabbinics, etc.) and then check indexes in that specific field. When you check a periodical index, use the volume corresponding to the year of the citation you are working on. Check the abbreviation list in that volume of the periodical index but also search that volume of the index by author for the specific citation. In this way you bypass the abbreviation. Do this because a significant percentage of "really hard to find" abbreviations are typographical errors.
Subject specific encyclopedias often include abbreviations which are useful mostly because they include not just journals but reference works and primary sources on a specific topic. The key is to determine which encyclopedias match the subject matter of the citation you are trying to decipher. By subject specific we mean something narrow like Augustinus-Lexikon (which has a nice abbrev. list on Saint Augustine), but of course broader works like Anchor Bible Dictionary may be appropriate sometimes.
Bible and General Theology
Elenchus Bibliographicus Biblicus is the most comprehensive bibliography for the field of biblical studies. It currently uses IATG abbreviations, but before 1995 each volume contained a list of abbreviations for secondary sources. The lists in ATLA, RTA, OTA and NTA are much briefer but more current. For primary sources the lists in BDAG Greek-English Lexicon of the NT and in HALOT Hebrew and Aramaic Lexicon of the OT are useful even though they are brief.
The Elenchus section of Ephemerides Theologicae Lovanienses is a major index for Bible and especially systematic theology. Some volumes list abbreviations for secondary sources.
Several church history indexes include abbreviations for secondary sources, including Revue d'Histoire Ecclesiastique (especially strong for 20th century, European, and Catholic history), Bibliographia Patristica (early church history), Sixteenth Century Bibliography and Archiv für Reformationsgeschichte (Reformation history).
Many of the larger theological encyclopedias have modest abbreviation lists. See, for example, vol. 11 of Lexikon für Theologie und Kirche for secondary sources, and vol. 1 of Religion in Geschichte und Gegenwart for both primary and secondary sources.
Ancient Near Eastern Studies
Context of Scripture translates many ANE texts, provides an abbreviation list and has secondary bibliography scattered throughout the volumes. Most volumes of the journal Orientalia have a "Keilschriftbibliographie" (Cuneiform bibliography) with short secondary abbreviation list. Remember the best approach is not just to check the abbreviation list, but also to use the index to locate the specific citation whose abbreviation baffles you, thus giving you the full citation. The journal Archiv für Orientforschung contains several bibliographies. The assyriological bibliography is in every volume; other bibliographies appear irregularly. Each volume of the Reallexikon der Assyriologie has a distinct abbreviation list of primary and secondary sources in Assyriology. Vol 7 of Lexikon der Agyptologie has a number of lists for both primary and secondary sources in Egyptology.
Judaica/rabbinics, DSS, Intertestamental and Early Pseudepigrapha
SBL (above) lists abbreviations for early Jewish works, DSS, and both Jewish and Christian pseudepigrapha, as well as journals and reference works.
Encyclopedia Judaica has articles on major rabbinic works and an abbreviation list in vol 1. Coverage of intertestamental (pseudepigraphical) works is weak. Introduction to the Talmud and Midrash does not have a single list of abbreviations, but it describes in detail most ancient rabbinic works, including Mishnah, Tosefta, Talmud, and Midrashim. It is often possible to find an entry similar to a given abbreviation. Be patient and you will be rewarded. On rare occasion Biblical and Judaic Acronyms is helpful even though it is mostly modern Jewish institutions and journal abbreviations.
Bibliography of Pseudepigrapha Research 1850-1999 does not have a primary source abbreviation list, but browse the table of contents of to find a primary source (and secondary bibliography). For DSS use Orion Center Bibliography of the DSS and Bibliography of the Finds in the Desert of Judah to find secondary citations and decipher abbreviations.
Classics and Greco-Roman Studies
Dictionary of Bibliographic Abbreviations Found in the Scholarship of Classical Studies and Related Disciplines covers secondary sources. Update with the list in a recent volume of L'Année philologique; bibliographie critique et analytique de l'antiquité gréco-latine. For primary sources, see the abbreviation lists in Oxford Classical Dictionary, Brill's New Pauly, LSJ/Greek-English Lexicon, and Checklist of Editions of Greek Papyri and Ostraca. The Thesaurus Linguae Graecae Canon does not have abbreviations, but it is a comprehensive list by author of Greek literature between Homer and AD 1400; if you have an ancient author, it is easy to browse for any abbreviated title by that author.
The Abbreviations.com is a large listing of all sorts of abbreviations.