How would I make a score board or how many enemies I killed?

You can do a simple score board with any of the GUI features, GUIArea, GUITextArea, GUILabel and then customize it with a GUIStyle

for example:

 void OnGUI() 
 {
     GUI.TextArea(new Rect(225, 580, 600, 200), "Enemies Killed: " + enemiesKilled.ToString(), fillStyle);
    }

Also see the GUI scripting guide: http://unity3d.com/support/documentation/Components/GUI%20Scripting%20Guide.html

but like whydoidoit said, its a bit vague what you want to do so if you could specify we can try and help you further.

hope this helped