1. Bad formatting.
"Formatting is more important than you know. Since decision makers are only glancing at your resume a few seconds before deciding whether or not you possess the knowledge and skills necessary to do the job in question, it's important to have your work history displayed in a way that will keep their attention long enough to extend an offer to interview.
2. Including an objective.
Often, they're just a waste of space--talking about what you want rather than what you can do for the employer. Since they're an older convention, they can make you look out of touch.
3. Focusing too much on just one job.
Sometimes this makes sense, but at a big company like Google, Yahoo and Microsoft, with hundreds or even thousands of openings, making your pitch exclusively for one job means you're less likely to be considered for other roles in which the company might think you're a better fit.