Few things can dampen the excitement of buying a new car more than getting short shrift on your old car's trade-in value. The used car market can be volatile, with trade values rising and falling more than the ratings on the newest season of “The Bachelor,” but that doesn't mean you're completely at the mercy of mysteriously fluctuating market factors. Fortunately, there are a few things you can do before putting on your game face and heading down to the dealership.

Knowledge Is Power
It's important to research your car's current trade-in value. That way, you'll have a better idea of what you can expect when it comes time to do business at the lot. AutoTrader.com recommends the Used Car Information Center at NADAguides.com, which will give you specific information on your car's current value based on factors like make and model, year and mileage information. Checking classifieds in the newspaper or online is also a good way to get a feel for what your car might be worth. Keep in mind that these prices are bound to include things like dealer mark-up, so be careful about considering these values too closely – the trade-in value you're offered is almost guaranteed to be lower than what you see others trying to sell your car for.

Keep It Clean
You wouldn't want to buy a dirty car, so why would you try and sell one? According to CarQuotes.com, a major factor in determining your car's trade-in value is the dealer's perception of the condition of your car. So not only will giving your car a thorough presale cleaning make it more attractive to buyers, you're also potentially increasing the amount of money you may be offered for it. Not a bad deal for the cost of just a little elbow grease.

Fix It Up
It should go without saying that if your car doesn't run, nobody's going to want to buy it. Trade-in time is the last chance to head into the shop for those repairs you've been putting off. Yeah, you'll be spending some money, but it's money you'll hopefully be making back by increasing your car's value. AutoTrader.com warns that you shouldn't be too careful here. If you spend more on repairs than would be added to your car's value, that's money you're not going to be seeing again. And most dealers expect used cars to have a couple minor peccadilloes anyway.

When the time comes for you to trade in your old wheels, make sure you head to NJ State Auto Auction. With hundreds of Carfax-certified cars on the lot, you're bound to find the car that's right for you.