I saw this gem of advice: ask for a candidate to explain his/her most significant accomplishment when sending a resume. (Found on Recruiting.com.) This is a great screening device (better than technical tests, in my opinion).
Candidates, this means you need to be thinking about your significant accomplishments (work-related please, unless you can make a real case for a non-work related accomplishment) and be able to write about them.
Hiring managers, you can use this as a screening device. If a candidate doesn't include a paragraph, you don't have to read the resume. Make sure your resume intake system allows you to grab the paragraph as well as the resume.
That is a very hard question to answer.