How should one give a gameobject to a prefab?

I have a prefab, and I have a gameobject in the scene which contains a script which I would like the prefab to access. As one cannot drag the gameobject in the scene on to a slot in the prefabs inspector what is the best way to go about this?

in Start()

go = GameObject.FindObjectWithTag("theTag").GetComponent<theScript>();

where theTag is the tag of the GameObject, use transform.Find or whatever else is needed if the tag isn’t unique. Assuming you want to access a script on the GameObject, replace theScript with the script name; get rid of that bit if you don’t care.