At the top of my resume/CV, I have a prominent "Note to recruiters" link which includes details on which kinds of companies I'd be a good fit for (and vice vers

At the top of my resume/CV, I have a prominent "Note to recruiters" link which includes details on which kinds of companies I'd be a good fit for (and vice versa), as well as other details (eg I'm not maintaining an entry in your database). This has proven very useful since you can immediately tell which recruiters have actually made an effort to qualify me, versus the ones indistinguishable from spam. I even go so far as to block the more egregious ones at my mail server which keeps the nuisance emails down.