Event called on prefab instantiate

When you instantiate a prefab the awake and start function are called. For example if you put this on your prefab :

 using UnityEngine;
 using System.Collections;
 
 public class Hello : MonoBehaviour {
 
     void Awake () {
         Debug.print("Awake");
     }
 
     void Start () {
         Debug.print("Start");
     }
 }

In the console you will see :

Awake

Start

In the case you want to set a parameter from the spawner to the spawned object you could use SendMessage like this :

 void Spawn () {
    Transform target = Instantiate(prefab, transform.position, Quaternion.identity) as Transform;
     target.SendMessage("Initialisation" /*, your param*/);
 }