Lowering rates
You may be able to negotiate lower corporate rates if you can guarantee reservations. Unlike hotels, most car rental agencies do not penalize customers who do not cancel reservations. This has resulted in an average 15% to 40% overbooking of reservations, and made fleet management quite difficult for the car rental agencies. By guaranteeing reservations, you can potentially knock off a couple of dollars per rental.

Drivers under 25
If you have many employees under the age of 25, negotiate ways to eliminate underage surcharges or waive an underage exclusion policy.

Mileage caps
If most of your firm's rentals cover a fairly limited area, you may be able to obtain a 100 miles/day cap in exchange for lower daily rates. In this case, you can get $4 to $5 per day off the standard corporate rate.

Corporate allowances
Make sure to negotiate what will happen if a retail rate is available for less than your corporate rate. Some agencies will allow you to default to the lower rate (or even less) under the corporate plan, while others will only let you switch if you agree to give up your corporate benefits.

Hourly rentals
Value is unique in offering hourly rentals in all its locations. A traveler in town for a brief business meeting can now pay as little as $1.59 per hour to rent a car, instead of having to pay a full day rate.