Having good neighbors means a lot. It's really worth going out of your way to cultivate good relationships. Keep up your house and yard. It really helps maintain the property values of the neighborhood when you see freshly mown lawns, shrubs that are trimmed and facade that is repaired in a timely manner.
If you live in a condo or townhouse, remember that sometimes walls have ears. If you have really noisy appliances, think twice before plugging them in on a shared wall.