There is no need to refrain from watching any channel, just keep the contrast/brightness on low for around 200 hrs. Once run in adjust settings to normal viewing levels.
You may find some image retention on occasions, especially if left on a static image for a considerable amount of time, but you should have a feature built into the TV which gets rid of any retention, this could be called whitewash or something similar, the manual should mention this.
Just sit back and enjoy your new TV and try not to get too paranoid about screen burn, plasmas are more robust than what you think.