And number all the pages. Definitely number all the pages. Dropping the thing five seconds before you're supposed to start... Eh, yeah, I definitely number the pages.
SMILE!
Unless your topic is of an extremely serious nature, smile. It will warm your audience up better than any joke.
Enunciate your words clearly. If you need practice in learning how to speak clearly, read the Dr. Suess book, "Mr. Brown Can Moo. Can You?" aloud a few thousand times.
Yes, it really does work. It seems a little less silly if you have a child to read aloud to.
Or join a church choir with a really good choir director, one who insists that you add the "d's" and the "t's" at the end of the words.
S-p-e-a-k s-l-o-w-l-y! It might seem like you're speaking at a glacial pace because you just want to get the darn speech over and done with, but your audience will thank you. Pause slightly between sentences.
You've been told to practice. I agree, but practice both reading your speech, and speaking off-the-cuff. That way, if you do drop your papers and mess up the order, or arrive at the podium with an entire page missing your speech will continue. As long as you don't apologize, and as long as it makes reasonable sense, no one will even notice. Believe me--been there, done that, got the t-shirt.
And while practicing out loud is good, mental rehearsal is just as important for me. I can imagine myself not only making the speech, but making it in the physical space where I'm going to be speaking, to the approximate size and make-up of crowd I'm going to be speaking to.
As far as interruptions go, how you deal with them depends on the type of interruption. You can ignore them, but realize that if something's bothering you, it's also bothering your audience and interfering with their reception of your message. You can politely ask that the interruption be dealt with and cease, if there's someone else who can take responsibility for dealing with it. This is especially important for long talks and on-going interruptions. You can, if you're confident enough and it fits in, make it part of your talk. I've done that a few times with preaching. If the interruption is the fire alarm, however, your talk is over. Get out of the building, eh?