#1 - Pretend You're Not NervousThis is probably the best tip I have. It sounds too good to be true, but it really works. I got the idea awhile back when I was pondering how actors act. Basically, I just pretend that I'm someone who doesn't get nervous. The butterflies in my stomach try to disagree with me, but I try not to listen to them (much).
#2 - Stare at the Back of the RoomThis tip I learned in my many years of high school and college choir, back in the day. Instead of actually looking into the crowd of people staring at you... look just above their heads at the back wall. They'll feel like you're looking at them, but you won't get the deer-in-the-headlights feeling that happens when you make eye contact with an audience member while you're nervous.
#3 - Take Care of Your Bodily NecessitiesIt's common to feel like you have to pee right as you're about to go onstage. I make sure I use the facilities before I even enter the room so that I can tell myself that that's only a psychosomatic reaction and not a physical one.
I also eat about 1/2 hour before a speech to make sure that I won't faint from low blood sugar (which hasn't actually happened to me in years, but it's a common fear I have when anticipating the worst that could happen while I'm onstage).
Above all, don't forget to breathe (both on stage and off), and definitely don't lock your knees. If you have to remind yourself of these things while you're talking, that's okay.
#4 - Pretend You're Only Talking to One or Two PeopleThis is another great tip I like to employ. I tell myself that I'm just explaining something to my roommate, my parents, my cat, instead of the hundred or more people that I'm actually speaking to. That helps me brain slow down and stop panicking long enough to formulate actual cohesive thoughts.
#5 - Imagine How You'll Feel an Hour From NowSometimes I like to play mind-games with myself, "Just think... in one hour, this will all be over!" (Substitute "one hour" for however long you have until your dreaded thing is actually over). For some reason this quells some of the pre-speech panic quite well.
#6 - Don't Practice Too MuchThis may not work for everyone, but for me it works quite well. I basically practice the night before until I have a general gist of what I want to say. Then I stop practicing. Over-practicing, at least for me, tends to cause more panic in me, which can lead to forgetting what I'm going to say.
What about you? Do you get nervous while giving a speech? What tricks do you use to get yourself through?