When looking for a limo, you want a company that will be honest and upfront about their costs and service....
Cost is a big factor, but should not be the only factor. While it might be enticing that one company's quote is considerably lower than other prices you have been quoted, there is probably a reason. Several limo companies serving the DC area will under price their limos for the sake of booking their vehicles. Often times, these companies will continue quoting and booking their cars, and over book. If you are their lowest priced event on a day they have overbooked, they might have "car troubles" or just not show up!
Service fees are often over looked in the total cost of a limo rental. Many limo companies will quote a rate that is lower than others, but will have additional fees. Sometimes these companies will charge tolls, gas, or mileage fees as well. Make sure to factor in all the fees when comparing different quotes you have received.
The most important and misunderstood(or misguided) fact is the number of passengers a limo can hold. Your typical Lincoln Town Car Stretch Limousine is a 120" stretch limo. That means the coach builder adds a 120" section to the original production Lincoln. The result is an eight passenger stretch limo. Most companies offer these cars as a 10 passenger stretch limo. Eight passengers is the official capacity of the car, and the most comfortable number of passengers.
Many limo companies have automated systems to answer their phone. This is geared toward their convenience, versus yours.
Good service should be rewarded! Many limo companies quote a rate plus an additional 20% service fee or gratuity. Some, if not all of that fee, goes to the company and overhead, not go to the driver. It is always good to "thank" your driver for their service.