The best way to get the best rate possible is to simply get a pre-approval with a CU such as DCU/NFCU/PenFed at a good rate and after negotiating price with the dealer let them know that you have a pre-approval. They may be able to beat the CU rate but I would get it in writing that they can only submit you to 1-2 of the banks they think can beat your interest rate through your pre-approval. I would fib a little bit about the pre-approval rate because if you tell them you have 4.5% for 72 they may very well come back at 4.25% for 72 and you might be leaving "money on the table."
Thing's that auto lender's like to see on your credit report are previous comparable installment credit such as a mortgage, previous car loans, personal loan, etc.
They obviously don't like to see previous reposession's or excessive utilization of credit cards.
As mentioned, do everything in your power to increase your score such as the AZEO method (all card's reporting a 0 balance except one card reporting a small balance under 9% of the utilization of that specific card)
