I’ve always been a big fan of just using whatever default font your word processor uses, because that’s what works for almost everybody in almost everything they write. So I don’t vary my font choices much; personal or professional, 99% of the time I get by with Times New Roman, 12pt font. No complaints so far. If I really have a mind to change things up, I’ll follow the book’s advice and just use a sans serif font for the headlines, and a serif font (usually Times New Roman) for the body copy. Beyond that, I really never need to change up the font, because most of what I write just needs to be easy to read—no bells and whistles necessary. Unless you’re designing a flier or pamphlet or something, nobody should notice your choice of fonts. The font isn’t supposed to matter. The important part is what the damn thing says.

Some say that 12pt Times New Roman is boring. I suspect that those people just don’t like reading and are making excuses.