Do read Moshe's How to give an OK talk, esp the Narrative part. It feels quite silly to repeat yourself on every slide but you are preforming live and not writing on paper - so tell the audience why slide N+1 is important and for the same reason as slide N at every opportunity. During my talk I felt as though I was being overly repetitive, but on watching it after the fact I feel like I didn't hammer home the point enough (you should do more shit like this!).
Speaking of speaking: I asked a few popular conference warriors (Martelli & Hettinger) how many talks they had given and when they first felt comfy giving talks. They didn't know. I should have asked Beazely and C.T. Brown but they're professors and get more practice in a year than most people get in a lifetime.
But seriously, those popular conference regulars didn't know. Hettinger estimated he had spoken 30 times. His wife then pointed out he did 15 talks last year and so he upped his estimate to "more than 15 twice." Martelli estimated 50-100 talks but was equally uncertain. Myself, I've only done 7-8 and still get nervous if the room is less than 30 or more than 300 people. Hettinger said something like "I still get nervy when it the audience is 10x what I'm used to." I couldn't coax an admission out of Alex (I had only vague thoughts on the topic when I asked, and no narrative).
Take it all as paraphrased hearsay, but anytime I have to step up to a podium I just say to myself "suck it up, princess." It mostly works.