Used Car Values
Determine the cars history.
When searching for a new or used car at car auctions or at car classifieds you find on the news paper or in the internet, it is always wise to gather the vehicles information to get enough information in determining the used car value. You may ask the used car dealer, or the old car dealer about the cars service and damage/accident history. This will give you an idea on what are the cars components that you need to pay attention to most often. For example, if the car has some issues with the engine always overheating, by knowing this in the cars history, you will know that the radiator needs attention. Thus, you will know that other used cars (without engine temperature trouble history) value will be higher than this car.

Cars Pricing
Don't be in a rush to purchase a car that you like. It is always advisable to do a little browsing first with all of the available resources, specially for those with a limited budget. As much as possible, get a list of the top 5 cars that you think you like and compare their car values and car pricing. Of course, everyone will want to choose the car that fits the lifestyle and the budget alloted for it.
Car Sites
Sites online that offers new or used cars for sale
It is alright to shop for cars online, though, you will only see the cars in pictures.

Before buying a car online, make sure that the site you are using is not a fraud. The second thing you need to do is to search for all the list of the cars, that are with in reach and with in the budget limitations, and make sure to contact the seller or the dealer of the car and ask for all the cars info. This information includes the car history (service and damage history), car pricing and the last price he/she is willing to offer, description of the car (feature, make, model, year, transmission etc) and more extra pictures.
Try to negotiate the price as much as you could and also negotiate the shipping cost, on who will pay the shipping. It is always best to visit the car, if possible, to make the decision easier. If you will visit the car, you will be able to see more details in to it and you might be able to test drive the vehicle.
Be patient in searching and buying for your next car.