I created a free template that gets as close as it can to standard screenplay format in Google Docs. Details on how to create your own copy and handle the formatting are included right in the template.
Access the Template
Click this link to open the template in Google Docs. Once on the page, click File and then Make a Copy and then save a copy to your Google Drive in whatever location you'd like.
Using the Template
The basic details on how to use the template are included at the top of the first non-cover page in red. You can delete these instructions when you are done.
Scene Heading = Title
Action lines = Subtitle
Character = Heading 1 (Ctrl-Alt-1 or Cmd-Option-1)
Dialog = Heading 2 (Ctrl-Alt-2 or Cmd-Option-2)
Actor Parentheticals = Heading 3 (Ctrl-Alt-3 or Cmd-Option-3)
Transition (Film Editing) = Subtitle, manually align right
ALL CAPS must be done manually as Google Docs doesn't support it yet. Manually add a second line after Scene Headings, Action Lines, Dialog Lines, and Transitions as Google Docs can't specify a full line after paragraphs yet. Google Docs doesn't yet support page numbering starting at 2 on the third page, so 1. appears on the first page.