By now, many consumers have heard of the federal government's Car Allowance Rebate System, commonly known as Cash for Clunkers. The basics of the program, like similar plans in several other countries, are simple: turn in a car that gets 18 miles a gallon or less and receive a credit of up to $4,500 toward the purchase of a new, more fuel-efficient replacement. (Trucks have separate benchmarks.) But like any multibillion-dollar program run by the federal government, bottlenecks abound. Information is available at the program's Web site, cars.gov, and here is a primer on how to avoid the administrative potholes: Q: Is my clunker eligible? A: The car must be no more than 25 years old, and its original mileage rating must be 18 mpg or less. (Check fueleconomy.gov to find the rating.) The vehicle must be in driving condition; it must be paid off and it must have been registered in your name, and insured, for at least a year. Q: Will I get a trade-in credit, too? A: No. The government rebate replaces the traditional trade-in credit. If the trade-in value of your car is worth more than the clunker rebate, trade your car in instead. Check Kelly Blue Book (kbb.com) to see what your car is worth. Edmunds.com also has a useful Cash for Clunkers Calculator at edmunds.com/calculators /clunker.html Q: What kind of car can I buy with the rebate? A: Any new car (including 2010 models) that has a sticker price of less than $45,000 and gets a combined city-highway mileage rating of at least 22 mpg Roughly half of all cars bought so far with the rebates have been domestic brands. Rebates cannot be spent on used cars. Q: What forms do I fill out? A: None. The rebate will be deducted from the sale price of the car you buy. Your dealer will handle the paperwork. Q: Can any dealer handle the rebate? A: Only certified dealers may participate in the program. To locate a dealer, check cars.gov/dealer-locator. Beware of Web sites that ask for personal information or offer to broker deals. Q: How quickly can I get my rebate? A: The rebate is deducted directly from the sale price of the vehicle. You should see this reflected on your invoice. But dealers must confirm that your car is eligible for a rebate. Because of the popularity of the program, this can take a couple of weeks, potentially pushing back the delivery date for your car. Q: What about taxes? A: In some states (including New York and New Jersey) consumers are taxed on the full value of the car, including the value of the rebate. That can reduce the value of the rebates by several hundred dollars. In other states, the rebates are not taxed. Q: Is the rebate the only discount I can receive? A: Absolutely not. Dealers are only passing along clunker rebates provided by the government. Many car companies are offering additional -- sometimes generous -- incentives, just as they would without the rebates. 'Deal with it like a regular transaction,' said Mark Schienberg, who is president of the Greater New York Automobile Dealers Association (gnyada.com). 'Go into the deal and make the best deal you can, regardless of the government rebate.' Q: What happens to my old car? Do I drive it to the junkyard? A: A trip to the junkyard is not necessary. Your dealer is supposed to ensure that the engine is destroyed so the car cannot be driven. Some dealers remove other parts, like fenders and glass. Others simply sell the clunkers for scrap. Q: How long will the program last? A: The government just approved another $2 billion, which is expected to keep the program alive for at least several more weeks. But the money is available on a first-come-first-served basis nationally, so act quickly. Some dealers have also stopped pushing the rebates because they have not yet been reimbursed for clunker rebates they already passed along. 