Most organizations agree that about 3 feet is a good clearance for most vegetation. But that is a rule that is not always easy to follow. Perhaps you like to plant close to the home, or maybe you have an older home that has more vegetation and old trees that you love, or what if you are taking advantage of passive solar heat? What then?
Eve if you don't have the ideal, cookie cutter situation, you can still use the principle of that rule. For instance, keeping tree limbs from over hanging the roof and keeping vegetation from directly touching the home is still better than letting it just grow wild.