Leave white space. Actors tend to read voiceover scripts while they are speaking, rather than memorizing the words. Leave white space by double spacing and leaving blank lines between sections. This helps the actor see the words quickly while speaking.
Use capitalization sparingly. All caps make a script difficult to read. If you write a word or phrase with all the letters capitalized, this indicates the actor should speak louder to emphasize the point. Don't capitalize the entire script because it will be confusing to the actor.
Punctuate. If you leave out punctuation marks, you ask the actor to guess when sentences end, when to pause, and when to exclaim. Put in proper punctuation, even though punctuation marks don't show during a voice over. The audience can hear the difference when punctuation is properly placed.
Use text special effects sparingly. Boldface and underlining can be used to indicate emphasis, but don't overuse these techniques. Technically, every word in a voiceover is important, so make sure you only emphasize words the actor might not otherwise think need to be louder.
Use numbers and symbols. Though most people are taught to spell out numbers when writing, in voiceover scripts the symbols simplify the reading process. The actor can glance at numbers and understand them. The same applies to symbols. Use symbols like % and $ instead of their spelled-out counterparts.
Show emphasis on difficult-to-pronounce words or proper names. Type the accented syllable in all caps. Examples: Mrs. CleMENT, Jim the HABerdasher.
Save documents in Microsoft Word format. Because many scripts are put on an electronic prompter, your Word document will allow the voiceover producer to type in changes. PDF files do not allow for changes.