instead of getting a credit card that you can go buckwild with, get a gas card from bp or whatever the local gas place is, it builds your credit the same as a name card, but you can't buy cd's and clothes and shit with it to where a year later you are maxed out and in debt up to your ears...buy your monthly gas with the card, every time you get gas put that money to the side, when you get the statement just pay the total.
Although when buying my house the people said it is better to have a little money used up on the credit card, because that shows you use the credit and it makes companies want to spend there time on you instead of having 6 cards layin around that you never use.
If you have one card and are responsible with it you should have no trouble getting a car, but keep in mind, it is much easier to get financed for a new car or house than it is for a used one just for the fact the bank feels safer putting it's money up for something that has immediate value if you don't make the payments, they can turn around and sell it and not lose alot.