Here are some suggestions for the speakers to make their talk a great talk!

• Be prepared!
• Know when and how you will answer questions. It sucks when one person asks a question in the middle of the presentation and the rest of the presentation goes to answering that question.
• If you're doing a presentation with multiple speakers make sure to rehearse once when you're both together. Also keep the number of people on stage to a minimum. I've seen quite a lot of presentations with 3 or 4 people on stage and it was always the one that had to say the least that spoke the most.
• Speak up and speak clearly.
• Make sure your presentation/demo works without internet access.
• 45 minutes is not that long. Choose some specific points you want to make and make them clearly.
• If your English isn't good do your presentation in Dutch.

Please add more suggestions in the comments if you have any.