I got this question recently:
“As a beginning screenwriter, I’ve come across conflicting advice about proper screenplay format. I’m using Adobe Story, which does the indents, etc. for basic categories, but I need help in dealing with special situations like subtitles and off camera soundeffects, as well as second-hand conversations imbedded in dialog. Can you recommend a reliable source of info?”
Never ever get caught up on formatting issues when writing a screenplay. Just tell your story and try and make the formatting as non-intrusive as possible. Try not to slow down the reading of your script using strange formatting or camera directions. Remember, when writing a early version of a screenplay you want it to read quickly and easily and be a page turner. Lots of crazy formatting can really hinder those goals.
Keep in mind, the screenplay form doesn’t have a governing body deciding what’s “right” or “proper.” We could all probably come up with dozens of obscure formatting needs that aren’t covered in any screenplay formatting guide – but again, try not to do this. If there is some real need in your story for some obscure formatting just format it so it’s easy to read and makes sense to the reader.
Final Draft is the industry standard so in general using it will take care of 99% of any formatting issues you might have. They have a free demo version available too, so you might try downloading that and typing in a few pages to see exactly how it looks in Final Draft for some guidance, even if you don’t want to purchase it.
Now to answer your question specifically.
I’ve seen subtitles done where the character’s dialogue is written out in English and then the parenthetical might say something like (in Spanish with subtitles).
Off screen sound effects should be written normally in the description. Something like this:
The sound of tires SCREECHING can be heard off screen.
I think second hand conversation would also be handled in the description. I can’t remember ever seeing this in a script so I’m guessing a bit on this one. Perhaps something like this:
In the background Mildred can be heard saying, “I can’t believe she really showed up.” The rest of the group agrees with a flurry of “yeah” and “I know.”
But again, no matter how you write it out just make sure it’s easy to read and doesn’t stop the flow of the story.