Which steps does government have to take to maintain full employment and low inflation?

In theory, this is simple.  In practice it is very
difficult -- otherwise, there would never be problems with inflation or high
unemployment.

Basically, to have both of these things,
government is supposed to keep the supply of money at the proper level and keep taxes
and spending at the proper level.  (Who knows what these proper levels
are...)

If there is too much unemployment, the government
is supposed to spend more and tax less.  It is supposed to (like the Fed announced it
would do today) increase the money supply by doing things like buying government
bonds.

When the rate of inflation is too high, the
government is supposed to do the opposite of all of these things.  Basically, it is
supposed to drain money from the economy so that there will be less
inflation.

This is a very basic answer to a very broad
question...