The way you have been told before is to refuse anything the finance-and-insurance person offers. The new way is best to listen to what the business manager has to say, some types of warranty coverages make sense.
The old school way of thinking is “Cash is King“. Some previous buyers believe that if you paid cash for your car you would get a better deal. That might be far from reality. Our advice is arrange your financing through your dealership, they can offer you a better price because the finance company gives them a kick back and would be willing to forgo some of it to you if you agree to there finance terms.
Most states offer no pre-payment penalties, so if you not satisfied with your current rate you can shop for better financing. Usually finance companies have a 45 day first payment schedule, so you have plenty of time to compare banks.