This is a major decision to make, as the style you choose signals readers that a new paragraph has begun. You really have only two options: 1) Indent the first line of your paragraph; or 2) Place one empty line of space between paragraphs and do not indent the first line.
Generally, paperbacks use the first method – indent the first line. The second approach, which mirrors the block style of a business letter style, is common in ebooks.
An indent of two/eighths to four/eighths of an inch usually is sufficient for the first line, though this varies depending on the typeface. This is how it would look in a paperback:
My jaw dropped. “How much?”
“About $5000. It’s a particularly nasty accusation your husband has made.”
“It’s not true, though.”
My divorce attorney, Alan Wagner, leaned forward, his broad shoulders stretching wide beneath his shirt. “We can win, I assure you. His strategy, though, appears to be to run your bank account dry so that you have no choice but to give in.”
For an example of block style, look at this article.
My name is Rob Bignell. I’m an affordable, professional editor who runs Inventing Reality Editing Service, which meets the manuscript needs of writers both new and published. I also offer a variety of self-publishing services. During the past decade, I’ve helped more than 300 novelists and nonfiction authors obtain their publishing dreams at reasonable prices. I’m also the author of the 7 Minutes a Day… writing guidebooks, four nonfiction hiking guidebook series, and the literary novel Windmill. Several of my short stories in the literary and science fiction genres also have been published.