Referncing variables such as OnTriggerEnter(Collider other) thumb rule?

Hello

I want to understand this, not the collider enter (this one is nothing) but other functions. aspecially my problem is when I call the function form another function. Two examples
Good idea:

...
ChangeSprite(item.spriteNeutral, item.spriteHighlighted)
}

private Void ChangeSprite (Sprite neutral, Sprite highlight)
{
//something here...
}

Bad Idea:

private void SetCollidingObject(Collider col)
{       
 if (m_collisionEnabled)
        {
            m_collisionEnabled = false;
            StartCoroutine(EnableCollision(collider col));
        }
}

IEnumarator(Collider col) //I want to be able to use the col var. in here
    { 
      if (col.gameObject.tag == "Item")
     {
      //something here...
     }
}

What are the thumb rules for referencing inside the brackets of the function?

Line 6 should read:

StartCoroutine(EnableCollision(col));

You don’t declare the variable type when calling the method - only when declaring it.