For years, I've been watching candidates' behaviors in their job search.  Some job seekers try to demonstrate how they "could" do the job, some demonstrate how they "did" aspects of the job applied for, and some demonstrate the evidence of how they have created value for their companies in the past, and would be able to create results/value for their potentially new employer.

Put yourself in the hiring manager's shoes for a minute.  Which type of candidate would you choose?...
Unfortunately, most job seekers put themselves into the first two categories.  You see, it takes the next level of thought to show your true value.  If you help the hiring manager understand that your mindset is focused on the same thing that theirs' is, you will relate to them a lot more effectively and build their confidence in your ability to successfully fill the role, bringing profit to the company.  You'll be speaking the same language, which comes down to dollars and cents of profitability.

Since most candidates do not take the hiring manager's concerns into consideration, the ones that do really stand out.  This thought process needs to be defined in your resume and your interview through examples.  Take some time to write down some of your accomplishments, awards, extraordinary performances, and translate that into value it brought the company.  The more specific your results are, the better.  However, that doesn't mean that you should lie and make up numbers if you weren't tracking your results.  Do the best you can with what you have, and make sure to track your results more carefully in the future.  It is a good idea to keep a document or folder electronically as a "brag book."  Be proactive, because with the economy going the way it has for the past decade, you should always be ready for the unexpected.