Be realistic as what can be accomplished and what can't. Most mortgage lenders require that the appraised value of the home be at least 20% higher than the mortgage. That gives them a cushion in case values drop. The appraisal is based on what comparable homes in your neighborhood have sold for. That's different than what homes are listed for sale at.
Check your credit scores.
Know what you want. There are so many alternatives from the standard 30 year mortgage. Mortgage rates and terms vary.
Shop around and compare mortgage lenders before you get mortgage quotes. Check the fees they require, time it takes, application procedures, points, and interest rates. It's amazing the variance you can find.