Both JV and jester are right on the money.
The order is up to you, mate!
I for one prefer:
Squats or deads (are alternated p/workout)
Chest (Bench, flyes, etc)
Chins and other lat exercises
Shoulders
Bi's Then Tri's
End off with 2 to 3 sets of abs (variety)
To answer your question exactly, I normally do the full eight weeks, but I am quite hedonistic
and don't quite believe that muscles grow better when surprised as some people have preached before (gladly not on this site).
HST is quite structured and it is the only program I know in which you know exactly how much you will be benching or lifting on anything in eight weeks time.