Consistency/Flaws: Is their title VP of IT but one of their duties is 1st level helpdesk support? Red flag! Is the format of their resume messy and distracted with misspellings and grammar mistakes? That person is automatically eliminated for jobs requiring organization and attention to detail!
Career Progression: Did they go from Jr Developer to Developer to Sr Developer... or from Architect to Developer to Team Lead to Developer, etc. Titles aren't the most important thing, duties are.
Details! Do they just have a company and title listed? Have they put time into describing their duties or just put down the most generic one-sentence description of a database administrator? Are there dates of employment? Watch out for a lot of 2005-2006, 2006-2007... this might only be a few months over the new year. The less details they include, the more likely they are to be hiding something.
When it comes to freelancers and temp workers, its very likely that they would have a functional resume with (2005-2006), just to not look like they are very inconsistent. Assignments end and another begins, which has been the case for a long time. Job titles are very subjective: Jr Media planner might have some of the same duties as a Media Planner at another company. Typos and grammatical errors are items then tend to stand out more and does point to lack of attention to detail.