You have to figure out what categories the denials fall into, and work on fixing those areas.
Are the denials because of bad demo info? If so, make sure that whoever is entering the demo info has accurate/current information, and is entering it correctly.
Are the denials because of incorrect coding/billing? If so, educate the provider/biller/coder on their errors, to prevent further denials. Modifier usage, MUE, LCD, etc, all come into play with that education.
Regardless of why the denials are happening, as Michele said, work them as quickly as possible. In my office, I rarely get denials. But when I do, they get corrected/worked and resubmitted same day.
What is your situation? Are you the in-house biller? Billing company? Something else? What sort of denials are you dealing with?