One of the peculiarities of the epigraphic profession is the use of arcane abbreviations and acronyms for the various publications. You can find a number of commonly uses systems below.
AIEGL NEW STANDARD
AIEGL, the International Association for Greek and Latin Epigraphy issued in 2020 a new comprehensive list of abbreviations that will be used in both SEG and BE. This is now expected to become the new standard: https://www.aiegl.org/grepiabbr.html.
Previous lists may be found at the folloing places:
SEG has a list at the beginnings of each volume, and on their on-line edition. For access via the University of Groningen library click here. A list may also be found here
The Guide de l'Épigraphiste has a list of abbreviations, available also as a downloadable PDF.
Claros/DGE has an extensive list on-line. Unfortunatelly access is not always possible. Keep trying!
Epigraphische Datenbank Manfred Clauss has a list that includes Latin inscriptions.
Authoritative lists of abbrevations for general Classics or Archaeology journals can be found e.g. in L'Année Philologique, the American Journal of Archaeology or the DAI Archäologische Bibliographie. A handy overview of the various systems is provided by the Berkeley library
