2. Yes, you need a script
If you think you can just wing it...don't. Write out your lines and be prepared. By this point in your games life cycle you should know it inside and out. Believe me when I say, when you see that little red light go on, it is like you are in Men In Black and Will Smith taps the button and there goes your memory. Also, be sure to write your script using your language. There is nothing more awkward than sitting down pitching your party game, sounding like Nicollo Machiavelli. Be yourself, but be prepared.
3. Use a professional
Realizing that I'm not a cameraman was the best thing that could have ever happen to me. It is almost guaranteed that you are treating your Kickstarter campaign as if it was life support. Making a game on a budget is tough. With that said, there are some things that you just have to pay a little money for. If you really know what you're doing behind the screen, then by all means, take a swing. But, if you just picked up a prosumer camera from Costco for this shoot, it is time to delegate. There is nothing more cringe-worthy than a poorly compiled video.
Though there are a ton of tips left unstated, these are the ones that really made our shoot awesome. The biggest thing to remember is to have some fun! You are doing some exciting stuff, make sure you treat it that way.