Technically speaking, an FHA loan would require just 3.50% down. A VA loan (if you or your spouse is a qualifying Vet) or a US RDA loan (if the home is in rural area as defined by USDA) would require no down payment.
However, Cameron's advice below is rock solid. The challenge of a mortgage is that it will be your largest debt, take the longest to repay, and cost the most compared with other debts.
A Marine staff sergeant buddy used to tell me the 5 "Ps" of the Marine Corps: Prior Planning Prevents Poor Performance. This maxim is especially true for mortgages... if you plan well prior to buying, you will create for yourself the best chance to succeed as a homeowner / mortgagor.
The former banker side of me prefers to see buyers with little or no debt, cash in the bank after closing (at least 3 months living expenses), and employment stability. Owning a home costs much more than the mortgage payment, taxes, and insurance. Maintenance, furnishing, improvements, and basic care (eg mowing the lawn) take money AND time.
What to do today: Obtain a copy of your credit report. The Federal Trade Commission hosts the site for one free credit report per year at http://www.annualcreditreport.com.
Look for any negative items on the credit report such as late payments, collections, charge-offs, etc. Some of these itmes might be old enough to be dropped (7 years for non-public derogatory accounts). Some might be innacurate. This web iste from the creators of the credit scoring model ( http://www.myfico.com
) will help you understand your credit report and provides advice on any corrections.