So, based on all that, here are the rather cut-and-dry Group C scenarios:
SPAIN, ITALY WIN: Spain wins group. Italy finishes second.
CROATIA, ITALY WIN: Croatia wins group. Italy finishes second.
IRELAND DEFEATS/TIES ITALY: Spain, Croatia advance. Spain is first with win or draw; Croatia is first with win.
But the fun starts if Italy wins and Croatia and Spain tie, as all three teams will have five points.
ITALY WINS, SPAIN/CROATIA TIE, 0-0: Italy finishes first because of Rule C (Azzuri scored two goals total against Spain and Croatia; the others will finish with one goal total in such a scenario). Spain finishes second because of Rule D above (Spain 5-1 in goal differential in all matches, Croatia 4-2). NOTE: There have been no scoreless draws in Euro 2012.
ITALY WINS 1-0 OR 2-0, SPAIN/CROATIA TIE, 1-1: Spain finishes first because of Rule D (goal differential in all matches). Croatia finishes second because of Rule D (if Italy wins 1-0: goal differential) or Rule E (if Italy wins 2-0: higher number of goals).
ITALY WINS BY TWO, SCORES AT LEAST THREE, SPAIN/CROATIA TIE, 1-1: Spain finishes first because of Rule D (goal differential). With 3-1 win, Italy finishes second because of Rule F (Italy is higher in UEFA coefficient ranking system). With any two-goal win bigger than 3-1 (4-2, 5-3, etc.), Italy finishes second over Croatia because of Rule E (total goals scored).
ITALY WINS BY AT LEAST FOUR, SCORES AT LEAST FIVE, SPAIN/CROATIA TIE, 1-1: Italy finishes first because of Rule E (total goals scored). Spain finishes second over Croatia because of Rule D (goal differential).
ITALY WINS, SPAIN/CROATIA TIE, 2-2: Spain finishes first and Croatia finishes second, both because of Rule C (goals scored in the matches between the tied teams).