If your credit score is 740 or higher, you will have access to the most desirable loan programs and best interest rates. Lately I have seen buyers with great credit using FHA financing over conventional because of the lower downpayment requirements with FHA. You should compare both options before you select your loan product.
If your credit score is between 719 and 739, it's likely your interest rate will be 1/8% higher than if your middle score was at least 740.
If your credit score is between 700 and 719, it's likely your interest rate will be 1/4% higher than if your middle score was at least 740.
For calculation purposes, the lender will select your MIDDLE score. The highest and lowest scores are both thrown out. It's a good idea to start monitoring your credit six months to a year before you plan to buy so you can get things cleaned up, as necessary. You can see that just a point or two difference in your scores can sometimes make a big difference over the life of your loan.
If you need a referral to a great lender, just let me know.