Some online video players give you the option to add or subtract delay e.g. by ±0.5s to subtitles to manually sync them to the video currently playing. However I become functionally dyslexic when it comes to actually figuring out how much delay has to be added. I end up randomly adding or subtracting delay and make it work through trial and error.
Is there some rule of thumb I could follow instead to systematically sync subtitles?
I usually just find a short isolated piece of dialogue (or the first spoken word) and count the time between the audio and the subs, whichever comes first. That usually gets me close to +/- 1s. Then I micro adjust from there.
You just gotta remember that a negative offset makes the subs appear earlier, and vice versa for a positive offset.