To my detriment, I don't do much preparation but I do think preparation is the key. I think if you have someone that could listen to your speech/argument before you give it, and then give feedback, this would be a good way to build confidence. I say "would" because I have never personally done this, but this is advice others have passed on to me.
Sometimes you are caught as a deer in the headlight.
The first time I did a bond hearing case, my supervisor comes up to me and tells me that I'm going in front of the judge in 30 minutes and the court house was packed. I said sure and was excited at the thought of it. Then I read the case file, the story was so convoluted, and there were so many nicknames of people part of the "alleged" burglary that I had to explain in order to make sense of the story I was going to present. I didn't even get a chance to talk to the accused client to get his side of the story. Then I realized that this big, burly guy's freedom was somewhat dependent on me.
So get up to podium: "Good morning your honor. This case is simple. It's one of mistaken identity." Pause. Shit. What the fuck am I going to say next. I'm not sure what I said next or how I got through it. I just remember explaining nicknames of the people from the story to the judge and confusing everybody, including myself. She let the client free on bond, but I swear it had to be a pity bond.
Immediately, upon seeing my supervisor, I apologized and said that in my mind I had a story I wanted to say and alibi I wanted to present. It just came out somewhat differently. She told me I did well. That I made the issue about something other than it really was to take the negatives away from the client. "Yes," I said, "That was all my grand strategy."