After a first look through of the combat system in the Dungeon Masters Guide, I boldly went to the gaming table thinking that I understood how to run things. Boy, was I wrong. Well, not necessarily wrong, mind you. But I froze up pondering potential corner cases in the system. Thank goodness that it was just a test encounter because the game ground to an absolute halt. I wasn't anywhere near confident enough to start make rulings since the intent was to run things according to the rules as written.
Determined to learn the way of 1st edition, I trawled the major old school forums looking for clarification. I didn't find a whole lot of specific advice but I did find some pointers. One such pointer was to ADDICT which is short for the ADVANCED DUNGEONS & DRAGONS® INITIATIVE AND COMBAT TABLE. Don't let the name fool you. It's not just a table. It's a step by step explanation of first edition's combat system with examples. It's a well done resource and it got me oriented but at times my head started to swim while reading. It is almost 20 pages of explanation after all.
After giving ADDICT a careful read-through I went back to the DMG. That really didn't help. The text there seemed ever more dense but I was determined enough to slog through. Then a lightbulb came on. What about OSRIC? I've had the PDF for years and even have the book on my shelf. I wondered how close it was to 1st edition. I never tried to play OSRIC but instead used it as a general resource supporting my other D&D-like games.
After reading the combat section in OSRIC I finally got it. I was already 80% of the way there but the clarity of presentation was invaluable. I now feel confident enough to start running the game and eventually work some of the niftier corner cases into my 1st edition gaming routine.
The AD&D 1st edition state machine is an amazing thing to behold but observing it to understand it is sometimes a bit difficult.