House parties should be "word-of-mouth" type of situations. Creating a Facebook event or making a flyer and sending it out to everyone in your Google Groups isn't the best way to go about getting people to show up. You have friends that will be punctual and show up at exactly the time you say, while others will stroll through after they've hit up 3 other parties and stay until the sun comes up. You don't need your guests and their randos in your apartment while you're in the shower getting ready for work the next morning.
To keep a steady flow of people at your party and have most of your guests there at a particular time, you have to give people different start and end times. Tell your time conscious friends to show up at 10 p.m. if that's the time you know you'll be ready. Tell your friends who are prone to tardiness to show up at 8 p.m. if you want the party to start at 10 p.m.