My typical approach is to write the paper in LaTeX, then (in a new file) to write the presentation in Beamer.
I am now getting to the point in my education/career where the first version of a paper and presentation won't be the last. The two will evolve together over some (hopefully not too long) period of time.
Is there a better way to handle this combined evolution? I already write all graphs and tables to file, so these continuously update, but are there any other techniques that help?