Harvey Balls (those little circles which are all white or quarter, half, three quarter of fully blacked out) and are one of those incredibly simple but powerful staples of any consultant's toolkit.
And it couldn't be easier to use. Each Harvey Ball is represented by a number, so you simply select the Harvey Ball font, and type 1 for a one quarter Harvey Ball, and 3 for a three quarter Harvey Ball.
You can read the full instructions and download the font here.
One of the problems is distributing your documents to people who have not installed the same font. Alastair provides detailed instructions for doing this, but I prefer to convert all of my documents to PDF format before sending them out to clients, which solves the problem more neatly.