Stop by your local bank
You'll probably shop around for your car, and you should do the same with your car loan. The dealer isn't the only place where you can secure financing.
Consider applying for a car loan at a local bank or credit union, especially if you have accounts with them. They can offer competitive rates, and you'll be able to enter the car dealership with financing already figured out. Plus, once a dealer sees that you are pre-approved, they may feel incentivized to find you a better loan through their finance department.
Don't rule out a co-signer
If, after shopping around for a car loan, you still don't have a good option, consider asking someone you trust — and who trusts you — to co-sign on a loan. However, understand that asking someone to co-sign on a car loan is a serious proposition.
If you fall behind on payments, your co-signer will be responsible for paying off the loan. Such a situation could negatively affect your co-signer's credit and your relationship, so be sure you're able to cover the debt before going down this route.
If, after all of the above, you still can't get a decent car loan, the best thing to do may be to put off car shopping and focus on improving your credit score. Avoid "No Credit Check" and "Buy Here Pay There" car lots; these predatory institutions could charge you upwards of 20% interest on your car loan, which isn't worth it.
Instead, build up your credit with some good habits. Pay all of your bills on time every month, pay down your credit card debt, live within your means and pay off what you charge in full each month, and save for a down payment.