To answer your questions:
1. Tap on existing networks. It could range from your first or second-degree contacts to sponsorship programs. Many companies, non-profits and open source organizations have programs which encourage community events. Look for one.
Also, social media would be key to generate interest. Register on Meetup and create a Twitter page.
If there are existing meetups in your vicinity, collaborate with them.
2. and 3.
Interactivity and participation is key to sustainable community model and isn't just limited to event day. Try to generate some interest on social media (Meetup, Twitter) through a poster, questionnaires and announcements.
During the event, allocate time for networking. Organizing an AMA can also help make things interactive.
Most importantly, involve folks who're interested enough to contribute to meetup organization. As you can guess, it can be a lot of work for a single person but will be a breeze when responsibilities are divided.
Last but not the least, have fun!