1) If you ever find yourself buffering on output, rather than making hesitation noises, just pause. People will read that as considered deliberation and intelligence. It's outrageously more effective than the equivalent amount of emm, aww, like, etc. Practice saying nothing. Nothing is often the best possible thing to say. (A great time to say nothing: during applause or laughter.)
2) People remember voice a heck of a lot more than they remember content. Not vocal voice, but your authorial voice, the sort of thing English teachers teach you to detect in written documents. After you have found a voice which works for you and your typical audiences, you can exploit it to the hilt.
I have basically one way to start speeches: with a self-deprecating joke. It almost always gets a laugh out of the crowd, and I can't be nervous when people are laughing with me, so that helps break the ice and warm us into the main topic.
3) Posture hacks: if you're addressing any group of people larger than a dinner table, pick three people in the left, middle, and right of the crowd. Those three people are your new best friends, who have come to hear you talk but for some strange reason are surrounded by great masses of mammals who are uninvolved in the speech. Funny that. Rotate eye contact over your three best friends as you talk, at whatever a natural pace would be for you. (If you don't know what a natural pace is, two sentences or so works for me to a first approximation.)
Everyone in the audience -- both your friends and the uninvolved mammals -- will perceive that you are looking directly at them for enough of the speech to feel flattered but not quite enough to feel creepy.
4) Podiums were invented by some sadist who hates introverts. Don't give him the satisfaction. Speak from a vantage point where the crowd can see your entire body.
5) Hands: pockets, no, pens, no, fidgeting, no. Gestures, yes. If you don't have enough gross motor control to talk and gesture at the same time (no joke, this was once a problem for me) then having them in a neutral position in front of your body works well.
6) Many people have different thoughts on the level of preparation or memorization which is required. In general, having strong control of the narrative structure of your speech without being wedded to the exact ordering of sentences is a good balance for most people. (The fact that you're coming to the conclusion shouldn't surprise you.)
7) If you remember nothing else on microtactical phrasing when you're up there, remember that most people do not naturally include enough transition words when speaking informally, which tends to make speeches loose narrative cohesion. Throw in a few more than you would ordinarily think to do. ("Another example of this...", "This is why...", "Furthermore...", etc etc.)