1.) Show your face. Get the principal crew all to contribute short, snappy interviews explaining their involvement in the project. Kickstarter is based on the human element and you need to show that you're a confident/competent human being.
2.) Keep it short. If I'm browsing on Kickstarter I'll give a campaign video about two or three minutes maximum to catch my attention. Remember that this is not your filmmaking manifesto, it is not documenting what you'll do with the money and it is certainly not a condensed version of your film. The point of the video is to attract investors and generate excitement about the project.
3.) Show some footage. Even if it's footage from previous productions which are in no way related to the one you're trying to sell, I want to see some footage that convinces me you aren't just a twelve year old with an iPhone trying to raise $20,000 to buy the RED. Personally I think that shooting teaser footage can work quite nicely but all you really need to show peoplemis that you know how to light and shoot. The rest can be explained in interviews.
4.) Be humble. You have to balance inspiring your investors with not coming across as arrogant or overly confident. Don't make promises you can't keep, don't over exaggerate anything about the film and certainly don't claim to be a better filmmaker than you are. People respond positively to honest, amusing requests rather than self involved pleas. Which brings me on to my last point...
5.) Be funny. No one wants to see your poker face in a campaign video. If you were pitching to a major studio you would want to be serious, but crowdfunding's a different game altogether. If you want casual investors, outside of your circle of friends and family, to invest then you need to come across as an appealing human being. 10,20 or 30 dollars isn't a huge amount of money so don't feel like you're convincing people to part with a huge amount of money- you're simply trying to get them to donate a small portion of their hard earned cash to your project. A smile and a well scripted joke can go a lot further than the best business plan. I would extend this point to say that your campaign video need not reflect the project. If there is a teaser trailer element then the tone should be the same as the finished film but even if you're makig a film about teenage abortion in flood victims you still need to come across as a decent person- just because the movie's depressing doesn't mean that everything you do in relation to the project needs to be a real downer.
These are just some thoughts I have
