I'm a little older, and I've bought over 20 new and used cars over my lifetime. Here are a few tips from my experience:
Buy CPO (Certified Pre Owned) vehicles if possible:
Awesome Rates
Better Warranty then New sometimes
Inspected properly and usually have a clean history
I got a 2011 QX from Infiniti, which is 74,000 brand new at the time, for about 49990 and I got a rate of 1.9 for 60 months, plus it had only 11000 miles and is covered for 7 years and 60000 miles + an additional year to make up for the year I lost, plus I got a discount on the total maintence package. With 15000 down, I'm paying 739 mo including all taxes fees and maintenence pkg. Which is insane, Had I bought new I'd pay well over 1000 a month.
Make sure you see the Carfax.
Even if you have bad credit, try yo pursue your own financing.
Take it to a mechanic you trust, any dealer will let you do it, but don't do this until your 99% sure you're going to buy the car. Because some dealers will request a non-refundable deposit to pretect themselves from people who re-neg.
An accident on a carfax is not the end of the world. By law a dealer has to tell you and unless the accident is described in detail, it may just be a minor fender bender, use it to get a few more dollars off.
Request the car be put on a lift, check for excessive rust and paint on the underbody which means the vehicle is painted. Rust and it may have been flooded.
Newer Cars >>>> Older Cars because the newer the model year the better the financing. I would take a newer car with high miles over an older car with low miles because you could purchase a warranty and maintenance pkg and still have lower payments
Negotiate the warranties, unless your buying a luxury car you shouldn't pay more than 1000 dollars total (including maintenence, warranty, tire and wheel etc.)
If you dropped or lowered your trade the value plummets.
If you put rims on your car, put the original ones on then trade it in, they are much more valuable on the streets.
Just a few things.