Captioning is usually considered when the video product is complete, if at all. Instead, the production should be filmed so that critical content does not appear where captioning will cover it (usually at the bottom of the screen). Captions should describe all of the visual content, including nonspeech noises. Suggestions for making attractive and functional captions include the following:
- Use a consistent style to display captions.
- Use one or two lines of text.
- Use a sans serif font, such as Helvetica, and proportional spacing.
- Caption the exact wording of speakers, including slang and grammatical errors. Occasionally, some edits may be necessary to facilitate reading speed.
- Describe sound effects that contribute to the understanding of the content.
- Use italics to indicate the narrator, off-screen voices, sound effects, and other vital information.
- Synchronize captions with the aural content.
- Do not often change the location of captions on the screen.
- Consult language style guide and dictionary for standard conventions regarding numbers, grammar, punctuation, and spelling.
This content and more information is from Creating Video and Multimedia Products That Are Accessible to People with Sensory Impairments .
-  Creating Video and Multimedia Products That Are Accessible to People with Sensory Impairments