In your opinion, what are the most important factors for an excellent presentation?
Some of the important factors influencing excellent presentations can include the following:
Understand your audience background, experience & expectations in advance (if possible).
Prepare the presentation slides / contents adequately e.g. include or breakdown the key contents into appropriate sections, use large font size text or picture, ensure good color contrast between text & background, ensure last few slides include summary of recap & next step action plans.
Prepare & rehearse adequately & seek feedback from colleagues / friends / supervisors etc. for further improvement.
Think of backup plan e.g. don't over rely on other's notebook, projector, laser pointer, whiteboard marker etc. will work on the day of presentation. You need to prepare for contingency e.g. bring your own notebook & projector (if needed), laser pointer, marker, spare hard copy of slides, spare soft copy of slides in thumb drive etc.
If possible, take a tour to the presentation venue one day before the actual presentation so that you are mentally & psychologically more prepared.
Stay calm & courteous during presentation, speak clearly & slowly, answer to your level best for all the questions from audience. For those questions you can't provide on the spot, promise to come back to them separately / offline. You might want to get someone to help you to jot down all the issues that you might need to comeback.
After presentation, give yourself a break & later reflect / ponder over feedback forms, what you'd done best & what areas you need further improvement - pen them down for future presentation improvement.