1) you need to prepare yourself: with good humour to take part in the interview, no matter how messy the situation is!!!
2) you need to show love and support to your kid: this's his first time to deal with the "judgement" from outsiders, if the teacher is rude/in-considerate/dark face to kids, go away without hesistation!!
3) you need to be punctual: don't be late, go earlier (half hour in advance--at least!) to get familiar with the school's environment
4) all by lucky, take it easy!!