Some good stuff from Tim Harford (although badly formatted - I suspect it looked better in the FT).
This is one I do already: don't file emails. "A fine research paper with the title “Am I Wasting My Time Organizing Email?” by Steve Whittaker and others at IBM Research concluded that, broadly, yes, you are. ... They found that an email search typically takes about 15 seconds, while a hunt through folders takes about a minute. (Some users also just scrolled up and down their inboxes; typically it took about 30 seconds to find an email!) Just to be clear: it took four times as long to find emails using the painstaking-to-set-up system than it did using the “archive and forget” system. Nor were “filers” any more likely to find the email they were looking for than “searchers”."
I have sympathy with this one too: "If you’d like to really aggravate a busy person, send them an email with an attachment saying “please see the attached letter”, and add no elaboration. This is a three-for-one communication catastrophe. First, you are impersonating the behaviour of someone trying to spread a virus. Second, your message is hard to read on a phone and, on some systems, is not searchable. Third, you’re slowing everything down. This isn’t a children’s treasure hunt, where each message points to the next message. It’s a failed attempt to communicate with a busy person."
And one to remember: "Be nice. You never know who will get to read your email – the jury at your fraud trial; the NSA; your partner; your boss."