It's bound to happen to you sooner or later: you go to a conference, full of enthusiasm, but are let down by one appalling session. Maybe it was unhelpful, told you misleading information or was just unbelievably dull! You can laugh about it later, but while you're in the session what do you do?
You can always get up and leave, of course; you will find that the vast majority of sessions at any conference will be helpful to you. However, if that is not something you are comfortable doing then it is good to know how to deal with a bad presentation as a member of the audience. Here are a few tips:
Be constructively critical with your notes
There is always going to be a reason behind every bad conference session. If the content of the presentation is not helpful, you will still be able to gain useful information by working out what has gone wrong, and how you can avoid it in future.
You should also leave similar feedback with them - being nice, of course - if you get a chance. Constructive criticism is always helpful, as long as you emphasise the constructive part, so you might be able to help make their next session a success.
Debate the points made
If you get a chance to ask questions, which you will at the end of most presentations, throw yourself into the debate. You will definitely find this more entertaining than the presentation itself, especially if you have formed some interesting points you are prepared to challenge the speaker about.
However, again the key is to be respectful. This isn't an excuse to argue or mock the speaker, but to raise issues with the content of their session. That way, you can make sure it is constructive and that everyone goes away having learned something, without any feelings getting hurt!