How to make a GameObject follow my Player

The correct way of vector3 distance is

 if(Vector3.Distance( selfObject, otherObject.transform) < distanceVariable);

tho following is much more complicated. Yet not complicated. Get the AI to look at the player and move Transform.Foward in that direction. More exact for your case you do something like this.-

  var enemyObject: Transform;
 function Update(){
    if(Vector3.Distance(transform.position, enemyObject) > 10)
    {
     transform.LookAt(enemyObject.transform);
     var dir = Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical")));
     if (dir != Vector3.zero)
         {
         transform.forward = Vector3.Normalize(dir);
         }
    }
 }

I hope I helped you at all.

This should help

http://www.youtube.com/user/TornadoTwins#p/c/11F87EB39F84E292/8/u8t3fdKhDxg

Hope it helps!