I have just answered this question~! Let me see if i can help you ^^
Because you are asking about English Oral Mock, I answer in English then ^^
Each school has different style on English Oral Mock, but maybe I tell about my school mock then.
My school grouped 3~4 people as a group, for 4 people you have 5 mins to prepare your oral and 6 mins for discussion. In each paper will have a situation given, for example:
"Your principle asked your group to prepare a orientation day, you may want to talk about..."
It can be debate a point of view and like the above --- asking opinions or organizing activities.
Few points will be given as tips and hints, I suggest you drop your points in note form but not in long sentences, this will waste a lot of time. You are also suggested not to look at the paper always while the speaking is started.
After that, each of the members will have one min talk. The teacher will choose a question to ask you and you need to response immediately.The question difficulties will be stated according to your expression and speaking in the group discussion. i.e. if you do well in the group discussion, you may ask to answer a more difficult question in one min talk.
Well~~ I may suggest that the hints and tips are not the most important during the discussion, this is because many of the groups have presented the same ideas already, and this will only make the teachers be dull. Therefore I think that the most important point in group discussion is the "Anything you want to add", you should show your creativity in the discussion so to let the teachers have a good impression to you.
I hope this can help ^^
Not copy, coz this is MY words^^