In one of my other posts I mention 'BurgZergArcade' (Peter Laliberte)
I highly recommend this extensive video tutorial:
1. Unity3d Tutorial - Health Bar 1/2
It currently has over 200 parts... Which is too much for some people.
However, he has made the scripts available for purchase for just $10.
Or you could watch the whole series & type it all out yourself... Which is... honestly, what I should do, to learn how everything works.
I bought them a while back, & I really should re-watch the tutorials. (I skipped from part 40 after purchasing the scripts)
243. Unity3d Tutorial - From Scratch Part A - Setting Up The Project
But yes. Certainly a keeper!