As a parent I always jot down some points to ask in advance, otherwise I'm likely to forget.
At secondary we find the parents teachers most need to see, don't bother turning up. The parents of regular/reliable/consistent/nothing to report students will in good-faith book an appointment with every single subject teacher. Art/music/IT/RE teachers quite often will teach 400-600 children every week, including 100-200 in each year. So parents' evenings can be a real nightmare.
I wish there were some two-way communication, so that schools/teachers of non-core subjects would let parents know "We are available if you want to raise any issues, but we don't need to see you if you're happy."