Disable your objects instead of destroying them; reinitialize them and enable them rather than instantiating new ones.

I have just started to use Unity and this was the first thing I wanted find out myself. There is a way to do this via the Resources.Load() method.

Firstly, create a new folder called Resources anywhere in your Unity Project. This folder can have subfolders. Now move your Prefab to this folder. Supposing that your Prefab is called "MyPrefab.prefab" you would do this (in C#)

private GameObject TestPrefab;

void Awake() 
{
    TestPrefab = (GameObject)Resources.Load("MyPrefab", typeof(GameObject));
}
void Update () {

    if(Input.GetKeyDown("space"))
    {
        Instantiate(TestPrefab,new Vector3(0,0,0),Quaternion.identity);
    }
}

I would suggest that it is probably best to use this sparingly. The Awake method seems like the most appropriate place to load resources.

unfortunately there is not any other way. you should create a public GameObject variable for each of those GameObjects and set that variable to the prefab in inspector. you can not find or get reference to prefabs by any means at runtime. (this is a big limitation that should be removed). keep in mind that when you say this.gameObject it will give you a reference to current instance so after distruction it will becom null.