If you've decided to lease rather than buy, you need to find the best deal.

The choice is easy if the automaker's offering a discount lease on the car you want through its finance company.

But if that's not the case, costs can vary a great deal from leasing company to leasing company. Virtually every part of a lease agreement is negotiable, so be prepared to haggle over fees, charges for excess mileage and other costs.

Here are some of the things to look for:

Acquisition fees

Leasing companies charge acquisition fees in the same way that mortgage lenders charge points. But they don't always spend much time talking about it until you're so committed to the deal that you'll go along with it because you're too eager to start driving your new car. It's usually included in your monthly payment. Ask about it. Make sure they show you what it does to your monthly payments and tell you what it comes to every month.

Capitalized Cost

This is the price of the car, plus any acquisition fee or other charges and minus manufacturer rebates or other discounts. Make sure you understand and agree to everything that goes into calculating the cap cost.

Residual Value

This is what the leasing company estimates the car will be worth at the end of the lease. How much you pay for depreciation is determined by subtracting the residual value from the cap value. Regardless what the actual value of the car is after two years, the residual price is what you can buy the car for at the end of your lease.

Open- and Closed-End Leases

Make sure you get a closed-end lease. At the end of a closed-end lease you hand over the keys and walk away. With an open-end lease you could wind up responsible for any difference between what they estimated your car would be worth at the end of the lease (the residual value) and what it is really worth.

That can cost you a great deal of money. The leasing company might lure you into the deal with a low monthly payment based on an overly optimistic residual value and then stick you with a big make-up payment when you return the car.

Monthly payments

Monthly lease payments cover:

• Depreciation on the car.
• Interest on the loan the leasing company used to buy the car.
• And in most states, sales tax on the amount you're paying for depreciation.

Since lease payments are made in advance, your first payment will be due the day you sign the contract.

Disposition Fee

This covers the cost of selling or getting rid of the car at the end of your lease. Know what it will be and ensure that the fee is waived if you decide to buy the car rather than return it.

Mileage

One of the most important parts of every lease is how many miles you'll be allowed to put on the car while it's in your possession. Don't sign-up for anything less than 12,000 miles a year. 15,000 miles a year is more realistic for most drivers.

You can always negotiate for a higher limit, but the more you drive the faster you're depreciating the car, decreasing its residual value and increasing your monthly payments.

Penalties

Your contract will spell out extra charges for:

• Driving more miles than you were allowed.
• Returning the car with any damage beyond "normal wear and tear."
• Returning the car and getting out of the lease early.

It's critical to understand what kind of damage the leasing company looks for when you return the car and how much it will charge for everything from coffee stains on the upholstery to a dented door or crumpled fender.

Security Deposit

Some leases require a security deposit that's usually equal to or a little larger than your monthly payment. At the end of the lease any penalties and the disposition fee are taken out of your deposit. You'll get back whatever's left.

By Stef Donev

Interest.com Contributing Editor