The lower interest rate let's you have lower monthly payments and in order to qualify for lower mortgage rates you need to show your current financial situation stable. You can either lower your spending or increase cash inflow by working part time to get lower mortgage rates and so the lower monthly payments.
One method of qualifying for a lower mortgage rate is to have a good credit record. In order to do this, prove that you have cleared all you liabilities and have maximum home equity with no outstanding loans or mortgage payments. It is better to consult a mortgage broker in your area for an authentic advice.
While refinancing, try to get a lower interest rate that can be adjustable which changes with market conditions and fixed and remains constant throughout the term. Remember that you want a lower monthly payment more than lower interest rate.
If you are refinancing and extending your term so as to lower the monthly payment, avoid having your credit record pulled every now and then as your shop for mortgage rates. This will lower your credit score and it will be difficult to get a lower monthly payment.