I'm preparing my first campaign, but I've read post-mortems by people with experience. They say you need a video, because that's what most people want to look at (and it indicates more about the gameplay than a screenshot); and you also want to build up a list of supporters first and then ask them to pledge on the first day, because that will boost your campaign's listing and thereby attract more people and hopefully more money; and likewise you want to post updates as often as possible because that also boosts your listing rank. For example, see the following:
Indiegamestory.org
Crowdcrux.com
StarvingIndieDev
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