Write down everything you learned from doing this presentation. All the "mistakes" you think you made. This will help you sleep, knowing that the list is saved somewhere that you can refer to it the next time you present.

When I prepare, I usually go over the theme I intend to discuss. I try to remember all questions that I've been asked about this them and include them in my powerpoint or in my discussion notes. I also use a search engine and SSC forums to see if anyone has posted questions related to my presentation. That always gives me ideas for demos or slides.

I put together a powerpoint presentation, some demo code if necessary, and review it several times before the "big day." I find myself tweaking stuff, such as fixing typos, adding slides, rearranging slides, and deleting stuff that just doesn't make sense to me. Some people practice their presentations in a mirror, just so they can get used to saying it. I practice by running through it in front of a group (I use my SQL Saturday stuff as an excuse to train our developers and project managers in T-SQL).

I do this all about a week in advance so I know I can get a good night's sleep the night before the presentation. I eat a decent dinner, drink lots of water the day before. Then the day of, I also drink lots of water, make sure my presentation still works, then go to the event. I always use the restroom before presenting and always make sure to take a bottle or two of water with me so I can sip when I'm thirsty.

Little tricks I use to get people involved includes bringing candy or silly dollar toys to throw out to people who ask good questions.

I rarely present on subjects that I don't know very well. I prefer doing the intro stuff because I know it backwards & forwards and hardly have to refer to my notes. However, I've been creeping out of my comfort zone lately by presenting more intermediate stuff too. And I tell myself that it's okay if I don't know the answer to all the questions, so long as I know the answer to some of them.

The key to not killing your voice is to use an old acting trick. Don't breath into your lungs. Yeah, I know that sounds silly, but do this exercise while sitting at your desk. Breath in and out a couple of times, paying close attention to your shoulders. Are they moving? If so, you're breathing into the top of your lungs. Not only do you not have enough oxygen in your system to get through the presentation, but you're killing your voice because you're talking in your throat. The idea is to use your stomach to fill your lungs to full capacity. Think of a plunger in your stomach that's pulling the air deep inside you when you breath. Your shoulders should NOT be moving, but your stomach will be. When you speak, push the air out from your stomach.

It takes practice, but it's way easier on your throat than the way most people speak.