The best way to ensure you qualify to the lowest mortgage rates is to know and optimize your credit score through keeping your debt to income level as low as possible, preferably below 28%, not applying for any other types of loans in the six months preceding any mortgage applications, paying all your bills on time and making sure there are no mistakes on your credit report. Making a down payment of at least 20% (keeping your loan-to-value at least to 80%) is also an important factor in qualifying for a good mortgage rate. Then, shopping around with different types of lenders, both online and those in your area, will also help to secure the lowest possible rate.