The best bet would be to develop some substance that, when consumed, would allow the consumers to be controlled by certain noises. The substance could then be added to beer. At some point after enough of the beer had been consumed by the unsuspecting public, they could take over all the radio/television signals and broadcast the noises that would control the people to do whatever the government wanted.
This is a pretty risky plan though, so it is probably best to try it out somewhere else first. A mental institution would probably be a good source of test candidates.
I heard Canada already tried this