Inject more money into the economy ...people are irrational when it comes to money ..so tend to spend spend spend. This is what the US is attempting to do with the tax rebate, but it is not neccessarily always correct because people might start to save the money due to fears of the economy in the near future. Of course this is a only a theory, like a said before people could become rational and lose confidence in spending money.
So much more to do though