Hey, good to see someone else take an interest in casting matches, we've been running a bit dry recently. I looked through your video, and just some quick pointers:
1. I think you were focused on the individual ships a bit too much. I think it's actually we as current casters could do more of, but the problem is that for you, at points you had no idea where shots were coming from, and as casters it's our job to paint the exact picture of what's going on. Try being a bit more zoomed out and grabbing all of the action a bit more, not just what's happening on what ship at a time.
2. There's some pretty good hotkeys for observing, r and f make the camera rise and fall respectively when you're on free look. Also, hit T when you get into spectator mode, it pops up a bar above each ship showing health, which is both very helpful to you and your viewers at the same time.
3. Play the game. A lot. Know what each weapon does, not just what their main purpose is but what else could they be used for, learn what ammo goes best with everything. As a caster your job is not only to paint the picture of the action, but later to be able to tell those watching why the thing that happened happened, and what else could be done in certain situations. Not only does this make you sound smart, but it also helps the viewers learn and feel like they've gained something from your cast other than just entertainment (also you get a side benefit of being able to fill dead space in action if you're able to talk intelligently about every facet of the game).
All in all, I like the enthusiasm, keep at it. I do run a lobby once a week on Tuesdays (so, tomorrow) from 5pm-8pm that I cast at
http://www.twitch.tv/imagine42, sometimes solo, sometimes with a guest co-caster, feel free to stop by and check it out and see how some of us are doing things already!