I was recently looking through the old Q&A with Gary on DF and came across this post. I thought it was worth including here for future reference on the whole declaring actions question.
Dragonfoot-Q&A 1 from 2005
RobertFisher wrote: Gary, another question about your current OD&D campaign, if you don't mind.
How are you handling initiative & disrupting spells?
Are you using 1d6 for the DM vs. 1d6 for the PCs for initiative? Are ties rerolled or considered simultaneous?
Gary: D6 for surprise, 1 = 1 free round, 2 = two free rounds. D6 for initiative, ties meaning simultaneous attacks.
RF: Do casters have to declare that they are casting before initiative is rolled? If so, do they have to declare the specific spell? If the caster's side wins initiative, is he safe from disruption? If his opponent's win initiative, do they automatically disrupt his spell with any successful hit?
Gary: Yes, as I always require, spell-casters must announce their actions, name any spell they mean to cast. If they are successfully hit and damaged before it is cast, the spell is lost.
In other words, I am DMing those matters as I have for about 33 years now
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