What I do as a panellist is read through the papers when I get them and note down the important points, potential questions and queries. We also as a panel, have a brief discussion before the appeals about any unusual cases in particular and what questions we want to ask and divide them up to make sure they are; of course there are unforeseen issues that arise as well.
Normally, unless the papers are scant, the parents' oral case is not as important.
As a human being, I probably have a judgement about the case before the appellant steps in the room, however there have been cases which looked weak on paper which have been argued very persuasively. There are also cases which seem to have a reasonable argument but the parent provides no evidence and getting information is like pulling teeth.
I find that the appellants cases are not well prepared on the whole. We often get realms of papers saying the child is lovely and a hard worker and wants to go to the school but not saying WHY it is the best one for them. Then we get the negative ones; they have to go to Y Academy and can't go to X High School because there is bullying or the children nick stuff from the convenience store on the way to school. Of course the following week, the appellants for X High School say they can't got to Y Academy for the exact same reasons.
The other main category is people who appeal because they don't understand the admissions criteria and want to know why a child two doors down got in but not their child.
Quite a few appellants do not turn up at all, ranges from 20-50% and we can only then decide the case based on what we actually have in front of us.
I sit in London so we have quite a lot of appellants with English as an additional language. Sometimes they bring a relative or friend to translate and that's fine. Most people do bring another relative, friend or work colleague but not all.
It doesn't matter how you dress, no one will judge you. I try to rearrange the furniture so we are not shouting from one end of the massive table to the other and seat the appellants closer to the panel with the admissions authority further away, so we are not seen to be on their side. Most rooms tend to be quite formal though. Water and tissues (sadly) are also provided.