Hi Pete,
Forensic scientists are often called to testify as to their findings in an investigation - so we have a lot of experience of talking in front of other people. And, although you might not think it to watch some of us, most of us usually dislike this part of our work!
The best training I ever received on this subject taught me something that I never would have imagined in a million years - the audience (whoever they may be) are actually rooting for you to do well! Once I learned that little gem, testifying suddenly became a whole lot easier. The people to whom you're speaking are actually interested in what you have to say - and they will become more interested the more enthusiastic you are about your topic.
If you have a known time limit, try and figure out what it is that you are trying to get across to your audience and how much/how little time you will have available to you. It is usually best to begin with some sort of outline - essentially telling them what they will learn/be told during your talk. When you finish your presentation, go back over the outline once more as a sort of summary - basically telling the group what they have learned from your presentation. This doesn't have to be lengthy.
Don't have a set script. It can look very rehearsed - even if you have been rehearsing! Know your subject matter, and know what it is that you are trying to get across to your audience.
Try and speak slowly and breathe deeply. In high-stress situations, our hearts beat faster and faster as the adrenaline runs through our bodies. As a result, we get breathless and talk faster and faster - often unintelligibly! Although you might not want to, it is often better to stand up to give a talk, rather than sit down. We can use our lungs to much greater effect (read: projecting your voice), whenever we are standing up.
If you are going to be using props or your presentation board to illustrate certain things to your audience, be very careful that you don't turn your back towards them. If you have to do this, stop talking! If you turn your head away from someone, your voice becomes softer - making you very hard to hear and understand. The techniques we often use in the courtroom are: point, turn, talk. We point at the item of interest on the display board, turn back towards our audience (the jury), and *then* we start talking. Whenever we move on to another area of the display, we stop talking, and go through the same routine - point, turn, talk. Try and think about those teachers at your school who you think do a great job of engaging the students, and try to understand how they pull it off. It is surprisingly effective!
Once you have figured all of this out, practice your talk with a stopwatch. And then do it again, and again, and again. If you are running too long, consider reducing some of your material. If you are running too short, are you still talking too quickly, going too quickly over your materials/observations/interpretations, or did you not consider including some time for questions from the judges?
Also keep in mind the level of education of your audience. Whilst you may think that everyone older than you knows everything (trust me, we don't!), you know your work better than anyone - after all, you did it, right? Keep it simple, and explain technical terms as you think necessary. Watch the expressions of your audience. If they are interested or disinterested, it will show - and you can try different things (such as explaining terms they may not understand, or using your display board/props) to help.
Make sure that you smile and appear pleasant. Just the simple act of doing this can actually *make* you feel better - even if you feel as though you have a load of butterflies in your stomach.
And don't ever forget - the audience is rooting for you!
Good luck, and if there is anything else we can do to help, please don't hesitate to contact us.
Geoff.