If you have a good neighbor, you are a lucky person. You have someone who cares about your needs and your property, who is helpful in the little day-to-day situations that come up, and who is supportive in times of crisis.
A good neighbor is someone who, for instance, understands that your children may occasionally run across his lawn,- even though you tell them not to. He'll realize that children can be careless about things like that, and he won't make a big fuss about it unless it becomes a regular thing. In the same vein, he knows that you'll understand if some of the trash from his trash cans blows across into your yard. In other words, he is sensitive to the unintentional things that can happen. He doesn't make a big deal about them.
A good neighbor is also respectful of your property. For example, she asks your permission before doing anything that interferes with what's yours. This means she wouldn't plant a huge tree in between your houses without asking how you felt about it. If she wanted to put up a fence, she would let you know first. She might work with you to decide where it should be placed. Maybe the two of you would even split the cost.
A good neighbor would lend you some milk if you ran out. She'd give you a ride to work if your car was broken, and let your children stay at her house in the evening if you got stuck working overtime. You would do the same for her. Both of you would help make the other's life easier.