Some tricks I learned from Asia Commons, those are just suggested ideas, please feel free to use your own techniques:
Speed dating
The general host (moderator) introduce the open space technology for all and host a speed-dating, all participants should 2 mins talks with each other: the host will ask all participants to change seats every 2 mins with a bell notification, this way we could ensure that people could have equal opportunities to know each other, disregard their position or title.
Round Table discussion
All participants sit into different tables (say max 6 per table), the facilitators raise some questions for all participants, each table should discuss internally and delivery their point of view after 20 mins of discussion, after 20 mins, each table should have one representative to present their idea about those questions and leave all the discussion on CJU wiki page after that session.
Open Discussion
All participants sit in a big circle or horseshoe (U shape), the host could start with a controversial question and let everyone state their own opinion.
Oppose, agree or no comment
I've to confess that I don't know how to name this. :P basically we'll have a clear line with bipolar sign (indicate strongly agree and strongly disagree) on the floor. When the facilitators shoot the questions, all participants should choose their position and stand right by the line to show their own POV. Of course, the facilitators should ask some people about their choices.