Regarding the event format, there are two important rules you should follow: 1) be innovative and 2) don’t forget: the format should help you achieve the goal!
Depending on the target audience, the level of publicity, the grade of participation and the expected output; the different event formats should apply. Some popular formats are formal/informal policy discussion, debates, workshops, seminars/webinars, forums, stakeholder “maintenance” (meetings), press conferences, crowd-sourcing events, brainstorming and ideation workshops, kick-offs, launches, meetings, slams, hack-athon, world cafe, after work beer & many more.