Never use both a tab space (first-line indent) and an extra line space to separate paragraphs. One of Microsoft Word’s worst defaults (only on Windows, that is) is an added after-paragraph space, which leads to bad formatting since most writers prefer the tab key to signify a new paragraph. Delete the after-paragraph spacing unless you wish to signify a new paragraph with an extra line space, as demonstrated by all articles on this website.

Do not use the space bar for first-line indentations or the return key for extra line spacing. This is bad form.