Lists of do's and don'ts on getting published, finding an agent or annoying your editor do the rounds all the time, but this one is slightly different because it's based on genuine comments from editors and agents.
Recently a group of them got together and held a 'mass tweet' publicising some of the dafter author queries and pitches they'd received, and explaining why these were rejected, and what writers should be doing instead. The result is this helpful list of what to do and what to avoid, and this amusing article in The Guardian which reveals one or two of the wilder pitches. (I particularly liked the divine mandate.)
I've read in the past about writers doing extraordinary things, like filling their query envelopes with glitter so that it would fall out all over the agent and thus be remembered. Well, remembered it certainly would be, but I wouldn't rate their chances of engaging said agent to act on their behalf all that high.
The fact that agents are still complaining shows authors never learn. Which is depressing in some ways, but gives those of us who can put a business letter together a modicum of hope, and the rest of us a jolly good laugh.