Keep a folder (either paper or virtual) of everything having to do with your house. It should include the settlement statements from the purchase of the home, any refinances, and when you sell the home. You should also keep track of any improvements (anything that permanently increases the value: remodeling, new roof, new deck).
You will need all these to calculate the adjusted basis of the home when you sell it.
For more information see IRS Pub. 530 - Tax Information for Homeowners
