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Pretty obvious, but the wider your lens the easier it will be to handhold at slow shutter speeds. Image stabilization is similarly helpful, as it is forgiving of handholding yet doesn't compensate for subject movement.
As for the reception dancing shots (with light streaks etc.) my personal preference is so that everything in the picture is sharp but with added light streaks. To get that result, I like to start by temporarily turning my flash off and setting my camera settings so that pretty much the entire frame is black except the light sources themselves (which will create the streaks). You can use as slow of a shutter speed as you want, since only the light sources will be exposed without flash, so you don't have to worry about subject blur. Then just add your bounced/OCF flash etc to expose the whole scene. This technique ends up looking very different from what ppl like Hoffer/Chuck have been doing recently, so there are certainly many ways to approach this.