I didn't do the smart thing and shoot multiple complete practice takes before recording my first few videos, and I really regret that.
That's because when you're alone, talking to nobody (or to a camera, but that's basically nobody), you seriously overestimate how much emotion you're putting into your voice. And it may depend on your recording apparatus, but many of recording devises seem to drain some energy and emotion out of your voice (in addition to you thinking you're putting more emotion in than you actually are).
Now that I've made quite a few videos, I've long-since learned that you have to over-animate yourself a bit. When you talk with others casually you're probably doing this already, but when you're trying to keep your thoughts on what you want to say and how and nobody is around you, chances are you're more monotonous than you imagine. Don't get crazy or anything, but it's better to really drive emphasis and stress words more than you think you should, because chances are it may still not sound emotive enough when you're finally editing it anyway, haha.
I think it can be even harder if you're doing face-cam ad-libbing, because you have to have your brain chug along and be ahead of you in terms of knowing what words your mouth is going to create. I've transitioned to using a script now, and it's a whole lot easier when you don't have to use your brain as much and can actually listen to yourself talk and analyze yourself as you go.
