First, don't hire new employees until you absolutely have to. Worker's compensation rates are based, in part, on your payroll costs. Thus, a business owner who writes $900,000 in payroll checks every year will pay a lot more for worker's compensation than the business owner who writes $150,000 in payroll checks every year.
Second, install a safety program. Worker's compensation rates are also based on your industry's typical risk and where you stack up versus the number of claims you receive. While this doesn't help a new company much at first, reducing or eliminating accidents will pay off in spades as your company continues to grow.
Another way is to consciously look for ways to bring injured workers back to your workforce as quickly as possible, even if you have to offer light duty positions. This means the insurance policy saves on wage payouts. You get discounts in the future.