How to show damage, and damage effect when damage was deal??

my game is about player that do damage on enemy,i had finished script the health for enemy and the player reduced when damage was deal using collisionEnter, my problem is how to show how much the damage that deal to the player, and how to show the effect when damage was deal?? are this kind using GUI system or what... i'm very new in unity and sorry for my english...

http://unity3d.com/support/documentation/ScriptReference/Debug.Log.html

You can just output it to the console... If you want it to show with GUI, you can:

http://unity3d.com/support/documentation/Components/class-GuiText.html

And just put the variable name...

Pretty easy.