The big hint I'll give is check out the bar on day 1 and day 2. There are 2 quests that you must complete to get the true ending. Failing both quests gives the "bad" ending, and failing 1 quest out of 2 gives the "good" ending. Both quests start at the bar. Also do not choose to end the day early, that gives the default stay-in ending. The true ending happens when you can convince everyone to go to the party! Hope this helps :)