Many of the things that will help you get your loan paid off are agreed upon before the loan is even signed. You’ll want to negotiate your interest rate to the lowest amount you can considering your interest rate and down payment amount. You will also want to make sure that your interest rate is not a set rate all the way through, but one that is tied to the current principle, meaning it goes down as the principle amount goes down.
The last thing you will want to do is make sure there is no prepayment penalty. The last thing you want is to have your hard saved money go out anyway at the end of the loan due to prepayment penalties.
Now that you have that all set up, when you sign the papers, make an extra payment right away. This will start the ball rolling in getting your principle to start dropping and have the resultant affect on your interest. Then, continue paying extra each month towards the principle. This will become easier and easier as the interest rate goes down due to the lower principle. All of this will help you pay your loan off faster, which with the lack of prepayment penalties means you will be paying a lot less for your vehicle than would have otherwise been the case.