Never use both a tab space (first-line indent) and a paragraph space to separate paragraphs. One of Microsoft Word’s worst defaults, on Windows, is an added after-paragraph space, which leads to poor formatting, since most writers prefer the tab key to signify a new paragraph. Prefer the indent to the paragraph space in most writing. Online writing proves the most common exception, where the paragraph space, as seen below, is standard.
Do not use the space bar for first-line indentations or the return key for extra line spacing.